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Goodman, Camille --- "Acta Sunt Servanda? A Regime for Regulating the Unilateral Acts of States at International Law" [2006] AUYrBkIntLaw 3; (2006) 25 Australian Year Book of International Law 43

Acta Sunt Servanda?
A Regime for Regulating the Unilateral Acts of States at International Law

Camille Goodman[∗]

I. Introduction

Does a written or verbal declaration, made by a state official without any reciprocal commitment, response or acceptance, outside the context of formal negotiations, and to the world at large, give rise to a binding legal obligation? Since the 1974 judgment of the International Court of Justice (ICJ) in the Nuclear Tests Cases,[1] this question can be answered in the affirmative. Whilst doctrine has long been in conflict over whether or not to assign any legal effect to such ‘unilateral acts’, they have been in constant usage by states in the conduct of their day-to-day relations, and in the development of customary international law. International law has expanded and developed rapidly since 1945 and continues to do so, particularly as the burgeoning pool of actors recognised as subjects of international law, and modern methods of travel and communication, increase the ties connecting the subjects of the international system. Unilateral acts have expanded and developed accordingly, both as a common means by which states conduct international relations, and as an accepted practice recognised in doctrine and jurisprudence.

The International Law Commission (ILC) identified unilateral acts of states as a topic suitable for codification and progressive development at its 48th session in 1996. The Commission noted that although the topic was well delimited and had been the subject of academic writing, it had never been studied by any official international body; that states had abundant recourse to unilateral acts and there was state practice to draw upon in deducing legal principles in relation to them; that although several judgments of the ICJ had considered unilateral acts, there were uncertainties and questions in the dicta; and that the law of treaties could provide a point of departure for the work.[2]

Unilateral acts were accorded little or no binding effect at international law prior to the 1960s, but their existence and effect was increasingly acknowledged such that the ICJ could state in 1974 that ‘interested States may take cognizance of unilateral declarations and place confidence in them and are entitled to require that the obligation thus created be respected’.[3] The importance of states being able to place trust and confidence in the declarations of other subjects of international law is obvious. Franck has observed:

[O]n this shared mutual expectation rests the element of predictability that prevents relations between states in the nuclear era … from being chaotic and far more dangerous than they usually are.[4]

Although conventional agreements are the normal way of acquiring rights and obligations at international law,[5] as they permit states to reconcile divergent interests by negotiation and agreement, unilateral acts are an important addition to this system, indispensable when negotiation appears impossible.[6] Whilst states are obliged to co-operate, due to close social and economic links, the ideological divide can at times be wide, and the utility of the unilateral path becomes evident when a solution is needed, but negotiation is not forthcoming. During the tension aggravated by the Suez Canal affair of 1957, for example, the Egyptian declaration on the 24 April regarding free circulation in the Canal was helpful in re-establishing international confidence and security at a time when a treaty on the matter was not possible.[7] In this regard, it is also worth noting that the acceptance of the jurisdiction of the ICJ, under article 36 of the Court’s Statute, is undertaken by an engagement that is unilateral in form, and which by avoiding the necessity for a convergence of wills in fact encourages it.[8]

Unilateral acts play an important role of their own in a modern system characterised by both decentralisation and ever-increasing globalisation. Modern communication techniques have helped to make unilateral acts one of the most frequently used tools of state interaction, and ‘they weave, so to speak, the daily web of international relations’.[9] Unilateral acts occur frequently, and often go unnoticed and undisputed amongst the daily mill of international relations: actions such as recognition of states, governments or situations; pledges of voluntary contributions to other states or international organisations; and cancellations of external debts are all recognisable examples of accepted unilateral action occurring routinely in international law.[10]

Conduct of states involving trade, security, investment, and innumerable other matters takes place in many forms and under varying circumstances, and is conducted by representatives ranging from the head of state, to bureaucrats or local diplomatic staff. Unilateral statements of government policy regarding future intentions[11] often are made to foreign government officials or diplomatic representatives, to the local or world media, or within the domestic political context. Yet, although the existence of a rule of international law giving binding force to such unilateral declarations of a state’s intention has been confirmed in international jurisprudence, the contents of the rule have not been delimited. Statespersons considering issuing declarations on behalf of their country are now on notice that they are ‘not merely expressing a passing fancy, but pledging the good faith and credit of their nations’.[12] It is important that the parameters of this legal norm are established pragmatically, considering the nature, elements and legal basis of unilateral acts, in order to formulate a legal regime to which states may refer when considering issuing a statement of future policy.

Although the ILC has been considering this issue since 1996, it remains divided over the topic, and its progress has been slow.[13] The ILC’s Special Rapporteur, Victor Rodriguez-Cedenõ, has produced eight reports,[14] including a schema of 14 draft articles, many of which have been debated and accepted by the Commission. In addition, questionnaires were circulated to states in 1999 and 2001 seeking information about their practice in regard to unilateral acts, and reports compiled on the responses.[15] Yet despite this, the discussion of the topic at the 55th Session of the Commission, in July 2003, still centred largely on whether or not the topic was suitable for codification.

While some members of the Commission doubted the validity of unilateral acts as a formal category of international obligations, others recognised them as an important mechanism of international law, which play a substantial role in international relations.[16] However, it is disappointing to note that the Commission was still discussing the feasibility and methodology of the topic more than six years after it was originally proposed. This was reflected in the establishment of a working group on the topic during the 55th Session, whose mandate was to find a consensus on the definition and scope of the topic and the method to be followed in dealing with it:[17] a task almost identical to that already undertaken by the working group of the 51st Session in 1999.[18] Yet the necessity of the topic, the frequent use of unilateral acts in state practice, and their discussion in legal writings and judgments of the ICJ and other courts have been noted by the Commission since its first report on the topic,[19] and delegations to the Sixth Committee continue to emphasise the importance that they place upon the development of a set of principles applicable to unilateral acts, which they regard as an important source of legal norms.[20]

In his seventh report in 2004, the Special Rapporteur presented a study of the practice of states in respect of unilateral acts, in which he classified acts according to whether they involved the assumption of obligations, the renunciation of a right, or the assertion of a right or legal claim.[21] The eighth report in 2005 contained an exposition of certain unilateral acts that were considered to be suitable for a more detailed study, and a presentation of the conclusions which the Special Rapporteur was able to draw from these acts.[22] All the discussion generated by these reports points to the constant interest of states and commentators alike in deeper investigation of state practice regarding unilateral acts.

Evidence and analysis of state practice, and replies from governments to the questionnaires addressed to them will be of most importance to the ILC, but academic discussion on the topic would also assist the Commission in its task. Yet very little has been written on unilateral acts in the last 20 years, and it is submitted that a new, pragmatic approach is needed, consonant with the ‘clear trend in contemporary international law doctrine … away from juridical formalism, including … the old, positivistic insistence that a claimed rule … must fit into one or other of the preordained closed categories of formal sources of international law’.[23]

Described as ‘informal transactions of states’ in as much as they occur outside the formal boundaries of the treaty-making regime, unilateral acts are in no way of lesser significance than conventional agreements, and the realities of international relations reflect this. No less than conventional acts, unilateral acts consist in the conduct of states, created and underscored by the principle of autonomy of will of sovereign states, binding and interpreted in accordance with the fundamental principle of good faith. This paper provides an overview of the subject, analysing the nature, elements and basis of the unilateral act in accordance with general principles of law in order to formulate a suitable regime to regulate them. This will allow unilateral acts to take their place as a formal, legitimate source of international obligations, producing universally understood and recognised legal effects, and contributing to the stability and predictability that is the aim of regulation at international law


II. The Nature of Unilateral Acts of States

At international law states can acquire legal rights and obligations through an expression of will. International agreements, treaties and conventions feature prominently amongst the sources of law cited in article 38 of the ICJ Statute, however unilateral acts are not mentioned, and indeed, no ‘all encompassing, uniform and precise definition of unilateral acts exists’.[24] Yet it is well-recognised that states can acquire obligations over and above those assumed in treaty relationships, through informal conduct and transactions involving unilateral expressions of will.[25] The ILC has defined a unilateral act as ‘an unequivocal expression of will which is formulated by a State with the intention of producing legal effects in relation to one or more other States or international organizations, and which is known to that State or international organization’.[26] Unilateral acts are thus a particular form of manifestation of the will of a state,[27] apt to produce legal effects in the same way as any other conduct of a state.

The fundamental conditions for validity of a legal act apply at least as much to unilateral acts as to any other: the act must be imputable to a subject of the law, the object must be legal and the rules relating to will and form must be observed.[28] However, unilateral acts broadly defined constitute a complicated and extremely varied source of obligations that require some preliminary observations. First, the strictly unilateral nature of the act in question must be delimited, to ensure that the only acts under consideration are those that are unilateral both in form and in substance.[29] Second, it is necessary to consider the various categories of unilateral acts that have come to be recognised in international law, and any ramifications these classifications may have for a legal schema regulating unilateral acts.

(a) The autonomous unilateral act

The etymology of the word ‘unilateral’ (from the latin unus; one, latus; side) reveals that the unilaterality of an act is characterised not by the number of authors of the act, but by their position in relation to the norm created.[30] In bilateral or multilateral treaties, the authors of the acts will equally be their subjects, but in the case of a unilateral engagement, the authors of the act will find themselves the promisors of obligations undertaken in favour of the promisees of the norm.[31] For example, a joint declaration issued by the Presidents of Venezuela and Mexico, at San José, Costa Rica, on 3 August 1980, creating an energy cooperation program for the countries of Central America and the Caribbean, involved the assumption of legal obligations on the part of the declarant states for the benefit of third states that had not participated in the formulation of the declaration.[32]

Unilateral acts, like other legal acts, consist of two elements: the legal declaration, or formal undertaking (the instrumentum) and the substance of that obligation (the negotium).[33] Legal acts can thus be unilateral in form alone, emanating from a single manifestation of will, or they can be unilateral in both form and substance, not only emanating but also operating independently of any expressions of will made by other subjects of international law.[34] A declaration that is unilateral in form, such as those accepting the jurisdiction of the ICJ under article 36 of the Statute, or notifying other parties to a treaty of a reservation, may well be bi- or multi-lateral in substance, requiring some degree of interdependence with another document.[35] For an act to be an autonomous unilateral act, however, it must be independent in form and substance, such that it is sufficient to achieve legal effect without the intervention of any other manifestation of will.[36]

The difficulty in distinguishing strictly unilateral acts from legal acts made as part of an agreement is demonstrated by the Legal Status of Eastern Greenland Case,[37] which is often cited as an example of a unilateral act.[38] The Permanent Court of International Justice (PCIJ) found that a declaration by the Norwegian Minister for Foreign Affairs (known as the Ihlen Declaration), to the effect that Norway would make no difficulty over the plans of the Danish government for Eastern Greenland was binding upon Norway ‘beyond all dispute’.[39] Whilst many commentators consider that this was not actually a unilateral act, stating that the binding effect of this declaration was simply the result of the negotiating circumstances in which it was made[40] – that is, as a ‘response to a request by a diplomatic representative of a foreign Power’[41] – it could in fact have produced legal effects by itself,[42] and thus falls within the definition of an autonomous unilateral act offered above.

The analysis used to find the Ihlen Declaration part of a bilateral agreement can be misleading, for if one goes past the formal text of the declaration itself, it is often possible to find other texts that can be combined with that at hand, such that the concept of ‘external reciprocity’ can be used to find an agreement or bilateral nature in almost any seemingly unilateral engagement.[43] At the other extreme, multilateral treaties can be conceived of as a process of unilateral acts expressing consent to be bound, such as signature, ratification, or accession.[44] It is therefore necessary to retain sensible criteria, ensuring that all conduct of states tending to have legal effect is subject to a legal regime, and using logical analysis to avoid any attempt to bring into the conventional regime acts that do not belong there. If the act analysed could produce legal effect by itself, it does not need to be excluded from the category of autonomous unilateral acts sought to be regulated here.[45]

(b) Classification of unilateral acts

The variety of conduct falling within this definition still leads some commentators to question whether any universally applicable regime can be found for unilateral acts, in view of the widely-spread and varying nature of the obligations that they produce.[46] Such varied conduct as a declaration of war or neutrality,[47] recognition of a state or government, a declaration ceding territory,[48] and a promise to act or not act in a specified manner,[49] all constitute unilateral conduct, yet produce very different legal effects. Various attempts have been made to systematise these acts according to the legal effects they produce.[50] Some unilateral acts, including recognition, protest, notification and waiver, are generally seen to have acquired the status of customary norms of their own volition,[51] whilst others such as promises, declarations and assurances are more difficult to classify and remain subject to debate.[52] A short survey of generally recognised unilateral acts highlights the difficulties posed by attempts to render their validity and legal effects dependent on classification in a specific category.

Recognition is ‘a unilateral declaration of will whereby a subject of international law acknowledges the existence of a fact, a situation or a claim and expresses its will to consider them legitimate’.[53] Whilst acts of recognition are ‘unilateral in the strict sense of the term and are perhaps the most important type of unilateral act’, they have characteristics in common with waiver and promise, as can be seen in cases such as Eastern Greenland.[54] Whilst the Ihlen Declaration recognised a legal situation (Denmark’s sovereignty over Eastern Greenland), it also contained a promise (not to interfere with Denmark’s activities in this territory) and even a waiver (of any title to the territory). The declaration of the government of Colombia recognising the sovereignty of Venezuela over the Archipelago of Los Monjes can similarly be construed as recognition, promise or waiver.[55]

Waiver, or renunciation,[56] is the abandonment or relinquishment of rights. Declarations of neutrality could be classified as waiver, if not promise or notification. Similarly, negative security guarantees given by nuclear states to non-nuclear states, stating their intention not to use nuclear weapons against them, could be classified as waiver as well as promise.[57] Protest, by which a state communicates to another subject of law its objection to, or non-recognition of, an act formulated by the latter, has sometimes been seen as the corollary of waiver, and failure to protest has been found to constitute waiver, as in the Temple of Preah Vihear Case.[58]

The controversial question of ‘promise’ is yet another example of the difficulties presented by any attempt to put universal acts into formalistic categories. The cases described above have already demonstrated the frequency with which unilateral acts can be found to constitute promises, and yet more examples can be added to this list. Such diverse conduct as the Italian Law of Guarantees of 1871, recognising the inviolability of the Pope and promising him specific rights, the Declaration of the Government of Egypt on the Suez Canal, and declarations of the French government relating to the cessation of atmospheric nuclear testing (which were the subject of the Nuclear Tests Cases) have been considered to constitute promises.[59]

A perusal of the jurisprudence and doctrine on the subject thus shows the difficulty, and, it is submitted, futility, of attempting such formalistic classifications. As has already been established, unilateral acts are a manifestation of the will of states, the conventional rubric for conduct of states occurring outside a treaty regime.[60] Starting from this premise, the term ‘unilateral acts’ is a misnomer for what is actually just the conduct of states, and all conduct of states may attract legal effects at international law in so far as the international order provides. This approach is reflected in the statement of The Netherlands to the ILC that material classification is unimportant and that:

the contents of unilateral statements are not restricted to certain categories of subject matter … The content of the statement [is] of secondary importance for the purpose of producing legal effects. Of greater relevance are formal criteria such as the unambiguity of the statement and the objectified intention of producing legal effects.[61]

Accordingly, it is the instrumentum, or formal criteria, of the legal act that must be used to classify it, and on the basis of which it will have legal effects, not the negotium, or contents, which are too varied and produce overlapping classifications. To this end, a ‘top-down’ approach to legal acts, assigning conduct of a state to its correct place in the international legal system and then deducing any legal effect, is more logical than a ‘bottom-up’ approach, attempting to classify the conduct as being within a certain category of act, and to assign it legal effects on that basis. Using this approach, the place of unilateral acts in the international legal system can be established, and their effects more readily understood.

(c) The place of unilateral acts in the international legal system

Legal effects are produced at international law by international legal facts, to which international legal norms attach effects that create, modify or extinguish rights and obligations of subjects of the international system.[62] While everything that happens in the world is a fact or event, some of these are so important that they are taken into consideration by a legal norm, and these are legal facts.[63] Legal facts can be divided into facts of nature that create legal consequences (such as an earthquake producing a new island), facts caused by individuals but not imputable to a state (such as birth and death, or publication of a book), and facts caused by individuals that international law ascribes to a state.[64] The latter, which are international legal facts, can be divided into lawful and unlawful acts. Unlawful acts will either be refused any effect, or will entail the international responsibility of the state concerned. Lawful acts are the ‘manifestations of the will of States in the domain of international relations’ and produce legal effects in so far as the international legal order provides.[65]

Anzilotti points out that it is not the manifestation of will that produces the legal effect, but rather the legal norm, which attaches legal effects to the legal fact when the conditions of validity are fulfilled.[66] The four conditions of validity are those that the law generally considers as necessary for the validity of legal acts: a capable subject; an appropriate object; the requisite intention, free from vice; and the correct form.[67] When international legal facts fulfil these criteria, they can be considered ‘international legal acts’ with legal consequences.[68] Finally, these international legal acts can be divided into unilateral, bilateral or multilateral acts, according to whether the law attaches legal effects to the manifestation of will of one subject, or requires the concurrence of two or more.[69]

This approach provides the same conditions for validity of unilateral acts as for bilateral or multilateral treaties, consisting of general principles of law that are found in all the legal systems of the world.[70] It requires an analysis of the instrumentum of the act to determine its classification as an international legal act entailing legal effects at international law, and allows the applicable legal norms to attach such effect in accordance with the nature of the act. Of course, the instrumentum by which a unilateral act comes into existence differ from those creative of a bilateral or multilateral agreement, and this must be taken into account when the conditions of validity are applied to determine the existence of the act. In particular, the question of intent, central to the existence of a unilateral act, is of great importance.[71] It is thus necessary to review the elements required for the existence of a valid unilateral act, and the methods of interpretation to be applied to the instrumentum creating them, in order to progress toward the conception of a legal regime governing unilateral acts.

III. The Elements and Interpretation of a Unilateral Act

Unilateral acts may be the most frequent tool of state interaction, but if a state were to incur binding obligations as a result of every action, statement or conduct, state practice would be severely restricted and the international system paralysed.[72] Accordingly, certain strict conditions must be fulfilled before a legal fact is regarded as a legal act, producing binding obligations for the declarant.[73] In the case of conduct occurring in the context of bilateral and multilateral treaties, these conditions are extensively codified by the 1969 Vienna Convention on the Law of Treaties (VCLT),[74] and this text is a suitable source, methodology and even substance when considering unilateral acts.[75] By considering the general conditions of validity individually, and using the VCLT as a point of reference, the peculiarities and requisite elements of unilateral acts can be established, allowing the development of some basic principles governing their interpretation.

(a) A capable subject

In order to be recognised in international law, an obligation must be undertaken by a subject of public international law, acting through an organ competent to engage the state.[76] In the context of unilateral acts, the state assuming the obligation is the sole participant in the formulation of the act adopting it, and the particularities resulting from this must be taken into account in considering the capacity of an organ to represent the state.[77] The provision in article 7(2)(a) of the VCLT, confirming the capacity of the Head of State, Head of Government, and Minister for Foreign Affairs, to undertake binding obligations in the name of the state seems to be generally accepted in doctrine,[78] practice,[79] and jurisprudence[80] as being equally applicable to unilateral acts.

Although express authorisation of ‘special powers’, as described in article 7(1)(a) of the VCLT will be sufficient to render a representative capable of binding the state, in practice this will be an extremely rare occurrence in the case of unilateral acts. In modern international society, in which governments communicate frequently and maintain institutional relations,[81] there are many other state organs that participate in the conduct of foreign relations, and this is reflected in unilateral acts.[82] Whilst the ICJ has on several occasions considered the ability of other state officials to bind the state, it seems that a systematic survey of state practice in regard to the situations in which such officials can bind the state is required before any conclusive observations can be made. Nonetheless, it can be seen that the general principles encompassed by the provisions of the VCLT relating to capacity to bind the state are to a large degree capable of being used analogously in interpreting unilateral acts. Keeping in mind the restrictive approach referred to above, the principles of articles 8, 46 and 47 are also applicable in this context.[83]

(b) An appropriate object

The second condition is an appropriate object of the unilateral act, for no manifestation of will can make good an object or purpose that is materially impossible, or forbidden by law.[84] The fundamental rule that a legal act will be invalid if it conflicts with a peremptory norm of international law (jus cogens) is as applicable to unilateral acts as to conventional agreements.[85] Similarly, unilateral acts relating to the unlawful threat or use of force, embodied in article 2(4) of the Charter, and reaffirmed in many texts including the Manila Declaration on the Peaceful Settlement of Disputes,[86] will be null and void ab initio, and may actually constitute unlawful legal facts, invoking the international responsibility of the state. The object of a unilateral act should not conflict with that of another international engagement contracted by the state, or it may attract the international responsibility of the state.[87]

Materially impossible acts, and acts that are considered immoral, have also been suggested to come within the list of factors capable of depriving unilateral acts of legal effect.[88] There are many factors that could be considered in relation to the legality of the object and purpose of a unilateral act, but their overall similarity to the principles governing the legal effects of conventional acts is obvious, and was noted by a delegate at the Sixth Committee, who stated that ‘since the consent to be bound by a treaty and the consent to a unilateral act were both expressions of will of a state, it seemed logical that the same reasons for invalidity should apply to both types of statements’.[89] This observation goes beyond simply the object of the act, and considers also the manifestation of will, a third condition of validity – perhaps the most important element in a unilateral act – and one that is crucial to its juridical validity or nullity.

(c) The requisite intention

The classical definition of a legal act, as a manifestation of will to which a juridical norm attaches legal effects, clearly demonstrates the importance that the doctrine of state sovereignty has accorded to the role of intention in determining international legal acts.[90] A unilateral declaration is binding if ‘clearly intended to have that effect, and held out … as an instrument on which others may rely and under which the declarant purports to assume such obligations’.[91] International jurisprudence has shown intention, and communication of that intention to the intended recipient, to be the decisive element making a unilateral act binding:

When it is the intention of the State making the declaration that it should become bound according to its terms, that intention confers on the declaration the character of a legal undertaking, the State being thenceforth legally required to follow a course of conduct consistent with the declaration. An undertaking of this kind, if given publicly and with an intent to be bound, even though not made within the context of international negotiations, is binding.[92]

In this formulation, unilateral acts are binding if they express subjective intent. This was the element by which the Court in Nuclear Tests distinguished them from non-binding obligations.[93] Yet the Court went on to state that the French statements had to be:

considered within the general framework of the security of international intercourse, and the confidence and trust which are so essential in the relations of states. It is from the actual substance of these statements and the circumstances attending their making, that the legal implications of these acts must be deduced.[94]

This statement appears to introduce an objective standard, whereby the decisive intent is not that of the French authorities, but that deducible from good faith, trust, confidence, and the circumstances in which the declarations were made.[95] It is thus necessary to decide whether it is the real or the declared intention that is to govern interpretation of a unilateral act: whether construction of the declarant’s intent is to be made on a subjective or objective basis.

The VCLT provides a largely objective system for conventional agreements, stating that ‘a treaty shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose’.[96] This objectivity can be taken further in the case of unilateral acts, for two reasons. First, unilateral acts are generally the expression of will of just one subject of law, of which it alone is cognisant, and is capable of expressing orally or in writing as explicitly as desired. Other states taking notice of this declaration can only rely on the declared intent, as they are not involved in the expression and communication of intention as they would be in a conventional process. Inversely, it may become important for the declarant state to be able to retreat behind the declared intention in limiting their obligation to that explicitly undertaken.[97]

The judgment of the Court in Nuclear Tests provides a further clue in the form of its statement that:

One of the basic principles governing the creation and performance of legal obligations, whatever their source, is the principle of good faith … Just as the very rule of pacta sunt servanda in the law of treaties is based on good faith, so also is the binding character of an international obligation assumed by unilateral declaration.[98]

This description allows us to see that intention is but a condition of validity, whilst good faith is, for the Court, the fundamental norm regulating the legal effect of the act. Logically, then, the condition of intention is subordinate to the fundamental norm of good faith, and thus when good faith demands it, an effective intention can be inferred such that legitimate expectation carries over intention.[99] If the action of a state, having regard to all the factors already discussed, objectively gives rise to the impression that it intends to be bound, then if necessary a legal fiction can be introduced to create the necessary intent and produce a binding legal obligation in accordance with the intention expressed.[100]

The ‘reasonableness’ of such assumptions obviously involves consideration of ‘the circumstances attending their making’,[101] and in this regard an analogy can again be drawn with the VCLT, which provides for recourse to such things as the preamble, annexes, and circumstances of the making of the agreement.[102] In the case of unilateral acts, any information contained in or attached to the declaration that does not directly communicate the action to be taken could be used as supplementary text for the purposes of interpretation.[103] The evidence that may be relevant in assessing a unilateral act includes all that that might throw light on the intentions of the declarant and the addressee,[104] and whether the circumstances under which the declarant acted were consistent with, or negated, manifestation of intent.[105] Most recently, the ICJ stated in the Frontier Dispute Case between Burkina Faso and Mali, that ‘in order to assess the intentions of the author of a unilateral act, account must be taken of all the factual circumstances in which the act occurred’.[106]

Another important facet of interpretation is the distinction between political and legal intent, or between the intention to create a binding obligation and a mere declaration of intention:[107] for only declarations by which a state intends to become bound acquire the character of a legal undertaking.[108] In the Military and Paramilitary Activities Case, for example, the ICJ stated that the intention of the Nicaraguan Junta to hold free elections arose as part of its political program of government, and refused to accord it any legal intent.[109] The precision with which the intention is stated is of great relevance to its interpretation. Jacqué argues that norm-creating intention is evident as soon as the object of an act is sufficiently precise, such that it is possible to identify any conduct that is not in conformity with the norm: under these conditions, he states, one finds oneself in the presence of a legal norm, and not a simple political desire.[110] The manifestation of will must be made in a clear and unequivocal manner, such that any conduct that contravenes the obligation undertaken will be identifiable.

It is also necessary to consider the presumption at international law against the renunciation of rights by a state.[111] As has already been discussed, the negotium of unilateral acts may result in a waiver, or renunciation, of rights, and as the ICJ pointed out in the Nuclear Tests Case, ‘when States make statements by which their freedom of action is to be limited, a restrictive interpretation is to be called for’.[112] In addition, any manifestation of will that is not made freely and without defects may be nullified in the same way as will is vitiated in a conventional situation: the provisions in articles 48 to 52 of the VCLT are a suitable source of reference in this regard.[113] Unilateral acts that are made as a result of error, fraud, corruption or coercion may be void ab initio, and the articles referred to above can be applied almost mutatis mutandis to unilateral acts. This overall system of interpretation largely retains the principles set out in articles 31 and 32 of the VCLT, which have been held to be general rules under international law for the interpretation of any legal instrument, from a treaty or unilateral act to an arbitral award or resolution of an international organisation.[114]

(d) The question of form

The final condition of validity prescribed by general principles of law is the form of unilateral declarations. First, as the ICJ pointed out in Nuclear Tests, international law imposes no special or strict requirements in this domain.[115] The variety of forms that unilateral declarations have taken in practice demonstrates this. The Ihlen Declaration was made orally, whilst the Suez Declaration was registered with the United Nations (UN) Secretariat. The French declarations in Nuclear Tests were made in a variety of circumstances including a statement by the French President at a press conference, and a declaration by the Foreign Minister at the UN General Assembly, and the Austrian declaration of neutrality was contained in a statutory document. Assurances by the government of the Third Reich guaranteeing the neutrality and inviolability of certain neighbouring states, which have often been considered to be unilateral declarations,[116] were made in the Reichstag or to diplomatic representatives of the countries concerned. When international law does not prescribe a particular form, the parties are free to choose what form an act will take, providing that the intention is clear,[117] because as international law is not in principle formalistic, it uses intention, rather than form, as the central element in the theory of a legal act.[118] In the case of unilateral acts, however, one crucial element of form has been retained: for a unilateral act to be valid, and opposable, it must have been adequately communicated to its intended audience.[119] This is a common-sense ingredient, for unless an act is known, it is of no legal value, and may be modified at will by the author.[120] Once such an engagement is made public, it acquires a definitive form and legal effect, and can be invoked against the declarant state by all interested states, if made publicly erga omnes, or by the pre-determined states to which it was communicated in private.[121] Publication, notification or communication of a unilateral act is thus of considerable importance, and can be compared to signature, ratification or adhesion to a conventional agreement.

These conditions of validity and rules of interpretation consist of general principles of law, applicable to all conduct of states, but adapted to accommodate the peculiarities of unilateral conduct. This system of construction limits the circumstances under which a unilateral act creates a binding obligation, in order to implement the intent of the declarant, and avoid the confusion, chaos and paralysis that would result in international relations if states were to become bound on an unregulated basis.[122] Having deduced the conditions of formation of a unilateral legal act, however, it remains important to discover what legal norm attaches to the act and gives it legal effect, or in other words why a unilateral act creates an enforceable duty in international law.[123] This remains a subject of debate, and the various principles suggested must be thoroughly canvassed in order to arrive at a suitable legal regime to regulate unilateral conduct of states.

IV. The Legal Basis of a Unilateral Obligation

The juridical rationale for unilateral acts has long been a point of dissension amongst publicists, and despite a clear indication from the ICJ on this matter in Nuclear Tests, it continues to be a source of controversy. Whilst the Court stated explicitly that ‘[j]ust as the very rule of pacta sunt servanda in the law of treaties is based on good faith, so also is the binding character of an international obligation assumed by unilateral declaration’,[124] doctrine is still engaged in a struggle between subjective explanations and the objective foundation of good faith. The subjective explanations offered range from a view that unilateral acts have no independent status or binding legal effect at international law, to theories that presumed consent, third-party beneficiaries of contract, estoppel and autonomous expressions of will found the obligation. These theories warrant exploration, for they cast light on various aspects of unilateral acts and highlight, by apposition, the truly objective basis of the obligation.

(a) No legal effect

The most restrictive view holds that unilateral acts have no independent legal status at international law, and that whatever their political value may be, they create no obligations in law. The French jurist Kiss stated categorically that a unilateral act does not engage the state from which it emanates,[125] although he acknowledged the existence of certain unilateral acts such as notification and renunciation, which he said give rise to pre-determined effects.[126] Similarly, Quadri examined both doctrine and jurisprudence on the matter and decided that neither has produced a result in favour of a unilateral promise being sufficient on its own.[127] These theories not only give pre-eminence to consent, but make it a criterion of the legal act, in so much as unilateral acts only become valid when they are quasi-treaties.[128] State practice and jurisprudence have shown the weakness of this theory and doctrine has accordingly ‘undergone a slow, yet significant, change’.[129] The theory that unilateral acts create binding obligations has experienced a steady increase in support.[130]

(b) Presumed consent founds the obligation

Even those supporting the binding nature of a unilateral obligation still seemed to feel constrained to discover its basis in a conventional context, and the theory of presumed consent was a popular one. By construing the behaviour of the addressee subsequent to the communication of the act as active or even tacit consent, a binding contractual relationship was implied.[131] This was considered by the ILC’s Special Rapporteur during the development of the VCLT, who stated that:

A possible explanation of the binding force of so-called unilateral declarations creative of rights against the declarant is to be found in the theory of presumed consent of the beneficiary.[132]

This reasoning is unsatisfactory for several reasons. First, the question arises whether silence or passivity is to be interpreted as amounting to consent, or to no more than indifference or forbearance.[133] Alternatively, equivocal reaction to a unilateral act may be construed as acquiescence, or absence of protest, and thus constitutive of an abandonment of a right.[134] This results in an onus being placed on the addressee to express contrary intent if it wishes to avoid the presumption of consent, producing a ‘constant negotiating posture’ which does not support the certainty of international law the ICJ was clearly seeking in Nuclear Tests.[135]

Furthermore, it is clear that the intention of the addressee is of no import in the formation or validity of a unilateral act: the only necessary intent is that of the declarant.

The ICJ stated unequivocally in Nuclear Tests that nothing in the nature of a quid pro quo, reply or reaction is necessary for a unilateral declaration to take effect.[136] To rest the binding force of a unilateral declaration on the presumed consent of the addressees – who may be the international community as a whole, if the declaration is made erga omnes – is to fundamentally alter the basis of the declaration. A strict unilateral declaration rests on the intention of the declarant, not on ‘any subsequent acceptance’ and thus consent adds nothing to the obligatory force of the act.[137] Presumed consent is unsatisfactory as an explanation for the binding nature of a unilateral act, and can best be seen as a legal fiction, used as a justification when the basis of unilateral acts was unclear, and the doctrine of consent seen as imperative in the existence of a binding legal obligation.[138]

(c) Third-party beneficiaries of contract

Another explanation for the binding obligation of the unilateral declaration is drawn from an analogy between rights conferred on third parties by a treaty, and unilateral declarations benefiting a second party.[139] This approach was taken by Sir Gerald Fitzmaurice during his work as Special Rapporteur for the ILC on the Law of Treaties. In a draft Convention on the subject he put forward article 22, governing unilateral declarations conferring rights on other states, which stated that:

Where a State makes a unilateral declaration in favour of, or assuming obligations towards, one or more, or all, other States, in such a manner, or in such circumstances that, according to the general rules of international law, a legally binding undertaking will result for the declarant State, the other State or States concerned can claim as of right the performance of the declaration.[140]

As this provision is contained in the same section as article 20, concerning the stipulation pour autrui, or rights or benefits expressly conferred on a third state by the treaty itself, the parallel being drawn in article 22 is obvious. In his commentary, Fitzmaurice explained that a third state can benefit from a unilateral declaration made by another state, if the declaration effectively creates legal rights.[141]

Although the provisions referring to unilateral acts were later removed from the draft, the principle of stipulation pour autrui was retained, and is encapsulated in article 36 of the VCLT. In the case of third-party benefits stemming from a treaty provision, however, the rights rest on a binding conventional relationship, rather than providing the basis for the obligation. Accordingly, acceptance by the third party adds nothing to the obligation already undertaken. The analogy with unilateral acts is self-evident: the theory of third-party benefit adds nothing to the obligation already contained in the unilateral act, and the binding nature of this obligation must be sought elsewhere.

(d) Unilateral acts enforced through estoppel

The municipal law concept of estoppel has often been invoked to support the legal effects produced by certain state conduct, and has been said to be the typical minimum effect of a unilateral act.[142] As a doctrine that prevents a party from acting inconsistently with a prior statement or conduct on the same matter, the effects of estoppel would appear to be identical to those of a unilateral promise.[143] A ‘minimum effect’ is quite different from a legal basis, however, and on examination estoppel, too, is unsatisfactory as the fundamental norm governing unilateral conduct. First, while the basic premise of estoppel has been generally transposed to international law as a requirement that states should be consistent in their attitudes towards given facts or situations,[144] there is no real consensus as to the form or limits of the concept, which is said to be substantially different in international and municipal law.[145] Indeed, MacGibbon has stated that, in its translation from municipal to international law, ‘the concept of estoppel has been broadened so substantially that the analogy with the estoppel of municipal systems may be positively misleading’.[146]

At municipal law, the concept of estoppel is related to the reliance theory of contract, and recognises the need to avoid injury to a party who has acted to his detriment in reliance on a promise. Common law promissory estoppel, and continental European ‘preclusion’ or ‘forclusion’ are all principles requiring some further formality, such as a seal, consideration, detrimental reliance, or causa, before a bare unilateral promise is enforced by the court.[147] The general principle of law deducible from the practical application of the concept at the municipal level is thus not one of ‘good faith’ but simply that promises are not enforceable unless reinforced by something further. International jurisprudence, on the other hand, has more often had recourse in a generic manner to good faith as the basis of estoppel in the international system.[148] Good faith is held up as one of the most fundamental general principles of law and plays a vital role in the international legal system, but the complex law of estoppel is not easily assimilated into international law as a ‘general principle of law’ under article 38(1)(c) of the ICJ Statute.

This is exemplified by the Case Concerning the Temple at Preah Vihear,[149] in which the Judgment failed to mention estoppel or preclusion at all. Judge Alfaro, in a Separate Opinion, discovered an ‘anti-inconsistency rule’, based primarily on good faith, which he distinguished from estoppel, preclusion and forclusion.[150] Similarly, in the Case Concerning the Arbitral Award Made by the King of Spain on 23 December 1906,[151] Nicaragua, which had formerly expressed its satisfaction with the decision of the King of Spain, was precluded from altering its position under the principle of good faith.[152] Despite there being no evidence of detrimental reliance or alteration of position on the part of Turkey, Russia was prevented, in the Russian Loans Case,[153] from claiming the interest on the principal sum of a loan of which it had demanded repayment, because in its diplomatic correspondence to Turkey it had continually referred only to the balance, and not the interest accrued.[154]

At international law, then, ‘it is questionable whether the common law requirement of action by one party to his detriment on the faith of a statement made by the other party will or should be regarded … as a necessary element’.[155] On another analysis, it has been suggested that every act of a state is probably intended as an act of self-interest, even if it causes only some imperceptible change in international relations, a power alignment or the thinking and policy formulation of another state.[156] In this regard, it can be seen that every act produces some consideration or reliance, as no state can act without having an effect upon other states.[157] However analysed, it seems that at its core, international law estoppel evidences the variety of circumstances and effects of an underlying rule requiring consistency of behaviour.[158]

This principle accords with ideas of stability of international legal relations, confidence in and protection of expectations, and will often produce the same effect as a unilateral promise, but the concepts of unilateral act and estoppel must still be seen to be distinct. This distinction is to be found in the way the obligation is created.[159] A unilateral obligation is created by a legal act, an expression of will by which the declarant unilaterally decides to be bound. Estoppel, however, results not from the intention of the declarant, but from the expectation or behaviour of the addressee of the act. Whether international law estoppel requires reliance or detriment in a manner analogous to municipal law, or only that the addressee believed in good faith in the reality of the obligation undertaken, the conduct of the third party adds nothing to the intention of the declarant, and the fundamental norm must be sought elsewhere.

(e) From subjective expressions of will to the objective foundation of good faith

Unilateral acts, like bilateral and multilateral engagements, consist in conduct of states, and are thus susceptible to regulation in much the same way as conventional acts. Just as the ultimate source of law in a treaty is the agreement behind it[160] – or the convergent expression of will of two or more sovereign states – so the principle creative of a unilateral act is the manifestation of will. This is reflected in the famous dictum of the PCIJ in the Wimbledon Case that ‘the capacity to undertake international engagements is precisely an attribute of state sovereignty’,[161] and applies equally to unilateral and conventional engagements.[162]

Attempts have been made to justify the binding character of both unilateral and conventional obligations on this basis alone: that is, that the foundation of the obligatory character of engagements undertaken by states reposes on the autonomy of will as expressed by a sovereign state or other subject of international law.[163] The argument put forward in support of this theory is that, while the principles of good faith or pacta sunt servanda may govern the execution of the obligation in question, they are insufficient to found the obligatory character of the engagement at its conception.[164] It is submitted, however, that it is precisely within the execution of the obligation that the basis of its obligatory nature resides, and that the manifestation of will creative of it is, as has been discussed above,[165] an important condition of validity, but no more. It is in the objective principle of good faith, and its more precise expression in other principles stemming from it, that the binding nature of engagements undertaken can be found.

This can be seen more clearly by looking at agreements between states from an historical perspective. From the earliest times, the expression of will constitutive of the conclusion of treaties was accompanied by solemn ceremonies, including the taking of oaths, intended to underline the importance, validity and sacred character of the obligation being undertaken, and the good faith supporting it.[166] Indeed, it has been suggested that the development of a principle such as good faith was inevitable in order to ensure the minimum co-operation and tolerance necessary for the emergence and growth of human society.[167] As the supernatural element waned, and the number of treaties concluded increased substantially, the moral principle of good faith was revealed as the heart of the matter, an essential presumption that the party both acted in good faith in agreeing to or acceding to the treaty, and would act in good faith in carrying it out.[168] The expression of will, as manifested by signature, ratification or accession, thus serves only to signify the party’s willingness to be bound. While this is an essential condition of validity, it is the good faith presumed to accompany the act that gives it binding force.

The decentralised character of international law, the increasing number of rights, obligations, and international actors, and the diminution in formalities accompanying international transactions, make good faith not only necessary, but more than ever an essential element in international engagements.[169] As formal treaties and multilateral conferences are replaced to some extent by electronic communications, it is necessary to be able to extrapolate the extent of rights and obligations that are created but not exhaustively delimited in these more informal situations. Evidently, this applies just as much to unilateral acts as to conventional agreements.[170] The questions thus arising are what is the content of good faith, how does it manifest itself within the area of international legal acts, and how does it operate in unilateral acts to allow states to draw such ‘proper conclusions’?

(f) Analogies with the law of treaties: the relationship between good faith and pacta sunt servanda

Good faith is consecrated in the law of treaties within article 26 of the VCLT, which is entitled pacta sunt servanda. It states that ‘[e]very treaty in force is binding upon the parties to it and must be performed by them in good faith.’ The relationship between pacta sunt servanda and good faith is rarely clearly explained, however, and the principles are often placed on the same plan of generality.[171] The rule pacta sunt servanda, which has constituted ‘since times immemorial the axiom, postulate and categorical imperative of the science of international law’,[172] is generally understood as meaning that valid treaties are binding on the parties to them; in other words, it is a command to execute an obligation, but does not actually determine the contents of that obligation.[173] It is a positivist rule with a specific application in the conventional domain, requiring that validly created norms are obeyed, as long as no norm-abolishing fact has occurred.[174] Where other norms intervene, however, such as impossibility of performance rendering an engagement useless, or a fundamental change of circumstances, the principle of pacta sunt servanda yields and the treaty-created norms in question become subject to a different regime.

Good faith, on the other hand, has a broader, but more removed role. It serves to delimit the contents of the obligation, to correct defects of will or formality where fairness demands it, and to enlarge the domain of obligatory acts in international law.[175] Good faith is the over-arching and reconciling principle of law that founds and legitimises other rules including pacta sunt servanda, rebus sic stantibus and estoppel.[176] It is possible to imagine the intervention of good faith to reconcile a collision of norms such as pacta sunt servanda and rebus sic stantibus, or to apply article 18 of the VCLT and decide whether or not a party’s behaviour was intended to defeat the object and purpose of a treaty. The obligatory nature of an international engagement can thus be seen to gain its binding force from pacta sunt servanda, which can be conceptualised as a specific enunciation of the application of good faith in the domain of international legal acts, with a fundamental importance of its own, but with its basis in the over-arching principle of good faith.

Good faith has been determined to be the ultimate legal basis of not only the conventional but also the unilateral act, the question of whether its more specific application in the form of pacta sunt servanda is similarly applicable to both has produced dissent. Some states and commentators have expressed the belief that the principle relates strictly to obligations created by pacta and that it is thus inapplicable to unilateral acts. The importance of the principle pacta sunt servanda has been recognised in doctrine in no uncertain terms: having been described by Anzilotti as ‘the basic norm from which the weighty chandelier of the law of nations is supposed to be safely suspended’. It is the basic principle of the law of treaties, ensuring that every treaty is binding on the parties to it, and must be performed in good faith.

Such a principle is equally necessary to ensure reliability and predictability in all forms of conduct of states, and thus it is suggested that the meaning of the term pactum should be extended in today’s international law to apply not only to bilateral and multilateral agreements freely arrived at, but also to unilateral acts of a legal nature.[177] If this norm, according to which engagements must be respected, is key to international legal relations, then to consider conventional agreements obligatory because they are founded on the concordant will of two or more states, while refusing to ascribe the same value to unilateral acts because the will is not met by another will, is a rigid and formalistic approach that does away with the very aim of regulation: the security and harmony of international relations.[178] Two further arguments can be made in support of this.

First, as previously stated, states acquire rights and obligations by an expression of will contained in the instrumentum declaring the undertaking, whether this conduct occurs in a conventional context (through a pactum) or by unilateral declaration. The separation between the instrumentum and the negotium of both conventional and unilateral acts has already been outlined,[179] and the similarity in the conditions of validity applied to determine the existence of a legally valid instrumentum creative of a treaty or an autonomous obligation has been observed.[180] Thus the term pactum could quite easily be extended to cover both conventional and unilateral acts without suffering any substantial change in its criteria. Second, and in the alternative, it has been suggested that a new term such as promissio est servanda, reflective of their autonomous nature, could be coined to apply the principle of pacta sunt servanda to unilateral acts.[181] Other constructions have included acta sunt servanda and declaratio sunt servanda,[182] and whilst such a maxim may not apply to all unilateral acts (protest, for example), it should be noted that the VCLT does not apply to all treaties, either. The term acta sunt servanda, which is the formulation preferred by the ILC’s Special Rapporteur on the topic, seems to give the most flexibility and to concord with the concept of unilateral acts as conduct of states. It is submitted that such a principle is necessary to give the certainty, stability and security to international relations which the ICJ was seeking in Nuclear Tests and that if it were synthesised in a pragmatic manner with the other elements considered above, it would be possible to elaborate an overall regime capable of regulating unilateral acts in a manner useful to states and to the international legal system.

V. A Legal Regime Governing Unilateral Acts

Having established the nature, elements and binding force of unilateral acts, a framework governing the creation and validity of a unilateral act emerges, which can be applied by states in considering whether and how to undertake a unilateral act, or in interpreting such an act.

(a) Regulating the creation and validity of a unilateral act

The similarity between conventional and unilateral acts, both in terms of the objective basis creating and regulating the obligation undertaken, and the general principles of law governing validity, have been highlighted throughout this paper, and analogies have been drawn with many parts of the VCLT. Whilst the principles of the VCLT are obviously not applicable mutatis mutandis to the unilateral regime, due to the distinctive characteristics of unilateral acts, many of those related to assessing the valid creation of a legal act are based on general principles of law, easily translated to the unilateral sphere. It is thus possible to begin by assessing the conduct in question according to general principles of law, to determine whether or not it is in fact creative of a legal act.

The act in question must first be determined to be an international legal fact, that is, an act imputable to a state, of a lawful nature, to which international law ascribes consequences in accordance with its norms. The norm in this case is acta sunt servanda, which will apply only if the international legal fact fulfills the conditions of validity for an international legal act – those of object, subject, intention and form – and produces legal effects autonomously, without the need for the intervention of any other legal act. Once determined to be a valid unilateral act, it will be a binding unilateral obligation, to be executed in good faith in accordance with acta sunt servanda.

The conditions of validity are largely the same as those for a conventional act, although somewhat narrowed in order to accommodate the autonomous nature of the act, and to maintain an interpretation of state conduct consistent with the rule against restricting the freedom of sovereign states.[183] It is important, however, to maintain an objective approach, interpreting the declared intention of the state in good faith, in order to achieve the security and stability of international relations, which is the purpose of the regime. To this end, the political and other circumstances surrounding the act may aid good faith interpretation. Intention to create legal relations is the key element to a binding unilateral act, but it is often difficult to distinguish between legal and political intent. In such a situation, the necessary intent may be inferred as a legal fiction if it appears that the act objectively gave rise to belief in a legal undertaking.

(b) The continued existence and execution of a unilateral act

Questions of revocation, suspension and termination require significant investigation, for the effects of unilateral acts are many and varied, and may certainly differ substantially from those of a conventional agreement. In this regard, once the instrumentum of a unilateral act has been assessed, and has been found to be binding in accordance with the principle acta sunt servanda, it may be necessary to look at the negotium or material substance of each act separately, and identify the legal effect it produces.

As no state can create an obligation for another state without its consent, the legal effects of a unilateral act could only be such that a state affirms a pre-existing right, undertakes an obligation, or, exceptionally, acquires a new right.[184] The latter may only occur if it does not result in an obligation for other states, in cases such as acquisition of sovereignty over a newly discovered territory, for example. An act of protest constitutes the affirmation of a pre-existing right, and seeks to prevent another state from acquiring or abridging it, while waiver of a right results in the acquisition of an obligation to no longer contest the right against the party to whom it has been waived. Similarly, recognition produces an obligation on the part of the recognising state to conduct itself in accordance with the situation, claim or competence recognised, and promise is an obvious example of an acquisition of obligations. Whilst the classification of state conduct into formalistic categories is not a useful approach, a practical assessment of the legal effects of the act may allow rules to be developed governing the negotium. On such a basis, it is possible to imagine the development of applicable rules similar to those in the VCLT governing modification, termination, suspension and revocation.

Unilateral obligations are more easily undertaken than conventional agreements, which require conciliation and concession, and thus they should perhaps be more difficult to alter or retract than their conventional cousins, in pursuit of the good faith co-operation that allows the international system to operate – although the reverse could also be argued. In any case, the maker of the unilateral declaration has the opportunity to insert conditions of revocation or modification into the original act, providing for an alteration of the obligation undertaken should stated events occur, or circumstances arise.

The over-arching principle of good faith is just as applicable to the unilateral regime as to its conventional counterpart, and thus nothing would prevent such norms as rebus sic stantibus, supervening impossibility of performance, or the emergence of a new peremptory norm of international law from affecting the continued existence of the obligation in much the same way as under the VCLT.[185] The VCLT provisions regarding internal law, territorial scope and non-retroactivity are also susceptible to translation into the unilateral regime.[186] Whilst the elaborate system governing reservation that exists under the conventional regime will not be applicable to unilateral acts, the formulation of reservations or conditions as part of the instrumentum at the time the act is created will need to be carefully enunciated.

(c) The unilateral regime in action

The framework set out above can be applied to real and imagined situations of unilateral acts, in a practical manner that exemplifies the greater certainty and stability that would result from a unilateral regime. One of the most frequently used examples of a unilateral act is that of guarantees from nuclear weapons states to non-nuclear weapons states, by which they provide guarantees of security or undertake not to use nuclear weapons against such states unless certain conditions exist. The Secretary of State of the United States, at the Conference on Disarmament on 5 April 1995, for example, declared that: ‘[t]he United States reaffirms that it will not use nuclear weapons against non-nuclear-weapon States parties to the Treaty on the Non-Proliferation of Nuclear Weapons’ except in the case of ‘an invasion or any other attack on the United States, its territories, its armed forces or other troops, its allies, or on a State towards which it has a security commitment, carried out or sustained by such a non-nuclear-weapon State in association or alliance with a nuclear-weapon State.’ What is the status of this declaration? By applying the unilateral regime, its binding character can be deduced.

The declaration was made on behalf of a subject of international law, in pursuance of a legal object, by the Foreign Affairs Minister: a person coming within the list of those authorised to bind the state. The intention was clearly expressed, and there is no evidence of any defect of will, in the form of error, coercion or fraud. Taking into account the particularities of detail included in the statement – which allow any conduct that contravenes the obligation undertaken to be easily identified – and the circumstances of its making, it is objectively ascertainable as a legal undertaking. There are no specific requirements of form, other than communication to the intended recipients, and these have been met. The statement of the United States Secretary of State thus constitutes a valid and binding legal obligation, which addressees of the act (non-nuclear weapons states who are parties to the NPT) are entitled to require be carried out in accordance with acta sunt servanda.

A unilateral act such as this should not be subject to arbitrary revision, and whilst this may be seen to limit the freedom of action of states, it is a consequence of the unilateral nature of the act undertaken. In any case, such restriction of freedom has been guarded against by the United States in this case, through the insertion of conditions in the declaration, providing for the termination of the obligation under certain stated conditions. Furthermore, rebus sic stantibus, supervening impossibility and the emergence of a new peremptory norm would all produce determinable effects: for example, were international law to develop such that the use of nuclear weapons was considered contrary to a principle of jus cogens, then the declaration would be invalid in any case.

(d) Applying the unilateral regime to Nuclear Tests

The Nuclear Tests Cases remain the most celebrated, and most controversial, example of a unilateral act. The capacity of the subject, lawfulness of the object, and successful communication of the unilateral acts in Nuclear Tests are largely undisputed, but the question of intention is not.[187] Intention is a key condition in the creation of a valid legal act, but it is subject to methods of interpretation. These have been delimited as clearly as possible above, in so far as application is concerned they nevertheless resemble a discretionary power. Both the ‘actual substance of the statements’ and the ‘circumstances attending their making’ must be used to assess the legal implications of the act.[188]

The substance of the declarations was quite clear, the first stating simply that ‘atmospheric tests which are soon to be carried out will, in the normal course of events, be the last of this type’.[189] They do not mention criteria as to when or under what circumstances testing could be re-commenced, nor do they announce any intention to sign the Test Ban Treaty: elements which would have made the Court’s reasoning much stronger.[190] On the other hand, the statements indicated that France considered it would be technologically of no use to continue carrying out tests in the atmosphere because of its advances in nuclear technology, and allowed France to complete the current tests and fulfill its self-interests, as well as providing reassurance to the world at large.[191]

As regards the circumstances attending their making, those criticising the Court’s decision have argued that the attitude of the French government, which had always maintained that nuclear tests were a matter over which it had freedom of action, and its refusal to confirm to Australia that the undertaking to cease testing had been given, in no way indicated an intention to be bound.[192] Supporters of the Court’s view submit that the global objectives and expectations that this testing should cease, and the propensity of these declarations to bring France closer to global expectations of behaviour, as well as the ongoing legal dispute, aided the Court in its inference that the circumstances surrounding the declarations indicated intention to be bound.[193] This is supported by the statements made over a period of five months, before, during and after the final round of tests.

Given the authority of the people making the statements, the prominence of the subject at the time, and the number of times the statements occurred, the Court’s decision is reasonable in light of the objective criteria applicable in the determination of unilateral acts. Where necessary, intention can arise through a constructive ‘legal fiction’ to create a binding legal obligation in accordance with the declared intent, and thus were it in fact the case (as is probable) that France did not really intend to be bound, the requisite intention could still be deduced from the declaration. It must also be admitted, however, even by the most forceful proponent of unilateral acts, that the case involves ‘judicial avoidance of confrontation with political authority’,[194] for the questions of sovereignty, global ideals and politics that the Court was asked to decide were neatly side-stepped by this decision.

(e) Form of the regime

The form that a unilateral regime should take is an important question, and will require significant discussion amongst the international community in order to find a universally acceptable answer. Whilst some states have indicated their support for the idea of the ILC’s draft articles, possibly leading to a treaty on the matter,[195] others argue that the topic is more suited only to an expository study,[196] and still others feel that seeking to subject the conduct known as ‘unilateral acts’ to a single set of rules is not feasible.[197] It has been demonstrated, however, that the differences between the conditions and principles governing unilateral and conventional expressions of will are much smaller than they at first appear, and that it would be entirely possible to draft a system similar to that set out in the VCLT to apply to unilateral action.

VI. Conclusion

It is anomalous that while bilateral and multilateral conduct have been regulated, and unlawful unilateral acts have been recognised and codified within the area of state responsibility, lawful unilateral acts remain unregulated at international law. The codification of unilateral acts would be a significant progression towards the achievement of the general topic of ‘sources of international law’, which was identified as a global topic of codification by the UN Secretariat in 1949. The importance of unilateral acts is likely to increase.

Unilateral acts constitute the conduct of states of an autonomous unilateral nature, and they are thus susceptible to regulation in much the same way as bilateral or multilateral agreements. Unilateral acts can be identified and isolated from acts performed under the umbrella of a conventional relationship, the conditions that govern their validity can be deduced from general principles of law, and their binding nature discovered in the over-arching concept of good faith as governed from day to day by the principle acta sunt servanda.

It is now nearly a decade since the UN General Assembly invited the ILC to examine the topic of ‘Unilateral acts of states’,[198] and the fact remains that ‘[i]n the interest of legal security and to help bring certainty, predictability and stability to international relations and thus strengthen the rule of law, an attempt should be made to clarify the functioning of this kind of act and what the legal consequences are, with a clear statement of the applicable law.’[199] In this vein, it is heartening to see that at its 58th session in 2006, the ILC has before it for consideration a set of ‘draft guiding principles’ for unilateral acts of states.[200]

Using the existing law of treaties as a point of departure, taking a pragmatic approach based on general principles of law, and reviewing the significant state practice that exists in this regard, a set of draft articles codifying the law of unilateral acts should be a priority for the international legal community. Clear exposition in draft articles, or codification in a conventional instrument, would allow unilateral acts recognition as a source of international obligations, and provide certainty for states by giving unilateral conduct determinable effects.

[∗] LLB (Hons) BA (Int Studies) (University of Adelaide).

An earlier version of this paper was submitted as an honours thesis at the University of Adelaide in 2003 and presented at the Australian & New Zealand Society of International Law Conference in 2005.

[1] Nuclear Tests (Australia v France) [1974] ICJ Rep 253 and Nuclear Tests (New Zealand v France) [1974] ICJ Rep 457. The judgments in the two cases are essentially the same, and page references in this paper will be to the Australian case.

[2] Yearbook of the International Law Commission (vol II, part two, 1996) [245] and annex II, addend 3.

[3] Nuclear Tests (Australia v France) [1974] ICJ Rep 253, [46], above n 1.

[4] T Franck and E Weisband, World Politics: Verbal Strategy Among the Superpowers (1971) 120-21.

[5] Frontier Dispute (Burkina Faso v Mali) [1986] ICJ Rep 574.

[6] J Charpentier, ‘Engagements unilatéraux et engagements conventionnels: Différences et Convergences’ in J Makarczyk (ed), Theory of International Law at the Threshold of the 21st Century: Essays in Honour of Krzystof Skubiszewski (1996) 367, 371.

[7] Ibid 369.

[8] Ibid.

[9] K Zemanek, ‘Unilateral Legal Acts Revisited’ in K Wellens (ed), International Law: Theory and Practice – Essays in Honour of Eric Suy (1998) 209, 210.

[10] Other examples of unilateral acts provided by states to the ILC include: declarations concerning the delimitation of maritime boundaries (The Netherlands); declarations concerning use of natural resources, and involvement in military operations outside borders (Israel); declarations concerning the protection of property in Latvia and Lithuania (Estonia); protests over the Timor Gap Treaty, and the recognition of East Timor’s right to independence (Portugal); See Replies from Governments to the Questionnaire, ILC 52nd Session, UN Doc A/CN.4/511 (2000). Australia has also expressed concern that unilateral acts should be binding, giving the specific instance of a state requesting extradition promising that the death penalty would not be applied to the extradited individual (Statement by Kym Taylor to the Sixth Committee of the UN, New York, 5 November 2002).

[11] The term ‘policy’ is used throughout this essay to indicate a course of action or principle adopted or proposed by a government as an act or statement indicating legal intention.

[12] T Franck, ‘Word Made Law: The Decision of the ICJ in the Nuclear Test Cases’, (1975) 69 American Journal of International Law 612, 620.

[13] The ILC proposed the topic to the General Assembly following its 48th Session in 1996 as suitable for codification and progressive development.

[14] International Law Commission, First Report on Unilateral Acts of States, 50th Session, UN Doc A/CN.4/468 (1998); Second Report on Unilateral Acts of States, 51st Session, UN Doc A/CN.4/500 (1999); Third Report on Unilateral Acts of States, 52nd Session, UN Doc A/CN.4/505 (2000); Fourth Report on Unilateral Acts of States, 53rd Session, UN Doc A/CN.4/519 (2001); Fifth Report on Unilateral Acts of States, 54th Session, UN Doc A/CN.4/525 (2002), Sixth Report on Unilateral Acts of States, 55th Session, UN Doc A/CN.4/534 (2003); Seventh Report on Unilateral Acts of States, 56th Session, UN Doc A/CN.4/542 (2004); Eighth Report on Unilateral Acts of States, 57th Session, UN Doc A/CN.4/557 (2005).

[15] See Unilateral Acts of States: Replies from Governments to the Questionnaire, Report of the Secretary-General UN Doc A/CN.4.511 (2000) and Unilateral Acts of States: Replies from Governments to the Questionnaire, Report of the Secretary-General, UN Doc A/CN.4.524 (2002).

[16] See the Report of the International Law Commission on the work of its 55th Session, [272]-[273] UN Doc A/58/10 (2003).

[17] See the Report of the Working Group on Unilateral Acts of States, 55th Session UN Doc A/CN.4/L.646 (2003).

[18] See Official Records of the General Assembly, 51st Session, Supplement No 10 A/51/10 (1996).

[19] Official Records of the General Assembly, 52nd Session, Supplement No 10, [196], UN Doc A/52/10 (1997).

[20] See the Summary of the Work of the Sixth Committee, 59th Session UN Doc A/59/100 (2004).

[21] Seventh Report on Unilateral Acts of States, above n 14, [8].

[22] Eighth Report on Unilateral Acts of States, above n 14 [9].

[23] E McWhinney, ‘Legal Effects of Unilateral Declarations’ (1977) 71 American Journal of International Law 747, 748.

[24] W Fiedler, ‘Unilateral Acts in International Law’ (2000) IV Encyclopaedia of Public International Law 1018.

[25] See inter alia E Suy, Les Actes Juridiques Unilatéraux en Droit International Public (1962); A P Rubin, ‘The International Legal Effects of Unilateral Declarations’ (1977) 71 American Journal of International Law 1; R Jennings and A Watts (eds), 1 Oppenheim's International Law 1187-96 (1996); G Fitzmaurice, ‘The Law and Procedure of the International Court of Justice, 1951-4: Treaty Interpretation and Other Treaty Points’ (1957) XXXIII British Yearbook of International Law 203; Nuclear Tests Cases; Burkina Faso v Mali [39].

[26] International Law Commission, Third Report on Unilateral Acts of States, 52nd Session UN Doc A/CN.4/505 (2000), art 1.

[27] V D Degan, Sources of International Law (1997) 270.

[28] D Anzilotti, Cours de Droit International (French transl, Gilbert Gidel from the original Italian ed) (1929) 339.

[29] Fitzmaurice, above n 25, at 230.

[30] Ibid; P Reuter, ‘Principes de droit international public’ (1961 II) 103 Recueil des Cours 534.

[31] F Villagran Kramer, ‘Les Actes Unilatéraux Dans le Cadre de la Jurisprudence Internationale’ in International Law on the Eve of the Twenty-First Century: Views from the International Law Commission 137, 140-41, (1997).

[32] See First Report on Unilateral Acts of States, above n 14, [83].

[33] Second Report on Unilateral Acts of States, above n 14, [42] & [44].

[34] Suy, above n 25, 30.

[35] Jennings and Watts, above n 25, 1192.

[36] G Venturini, ‘La portée et les effets juridiques des attitudes et des actes unilatéraux des Etats’ (1964 II) 112 Recueil des Cours de l’Académie de la Haye 367, 400; Suy, above n 25, 34; Charpentier, above n 6, 371.

[37] [1933] PCIJ ser A/B, No 53 (hereinafter Eastern Greenland Case).

[38] Fiedler, above n 24, 1018.

[39] Eastern Greenland Case, 71.

[40] Rubin, above n 25, 4; P de Visscher, ‘Remarques sur l’évolution de la jurisprudence de la cour internationale de justice relative au fondement obligatoire de certains actes unilatéraux’ in J Makaraczyk (ed), Essays in International Law in Honour of Judge Manfred Lachs (1984) 462.

[41] Eastern Greenland Case, 71.

[42] Suy, above n 25, 126.

[43] M Virally, ‘Le principle de réciprocité dans le droit international contemporain’ (1967 III) 122 Recueil des Cours de l’Académie de la Haye 46; J D Sicault, ‘Du caractère obligatoire des engagements unilatéraux’ Revue Générale de Droit International Public, (1979) 634, 643.

[44] Zemanek, above n 9, 210-11; Rubin, above n 25, 8.

[45] Sicault, above n 43, 645; Suy, above n 25, 156; Venturini, above n 36, 400.

[46] J H W Verzjil, International Law in Historical Perspective (1973) 105.

[47] Eg the proclamation of perpetual neutrality of Austria by the Austrian Federal Constitutional Act of 26 October 1955.

[48] Affaires des frontières Colombo-Venezuéliennes 1 UNRIAA 223 (1922).

[49] Eg the Declaration of the Government of Egypt on Suez Canal (24 April 1957) 265 UNTS 299.

[50] Degan, above n 27, 285-86; G Schwarzenberger, International Law as Applied by International Courts and Tribunals (vol IV, 1957) 548.

[51] See eg Schwarzenberger, ibid 549; P Guggenheim, Traité de Droit International Public (2nd ed, 1953) 274-82; Jennings and Watts, above n 25.

[52] Fiedler, above n 24, 1018.

[53] Sixth Report on Unilateral Acts of States, above n 14, [48].

[54] Ibid [21].

[55] Note of 22 November 1952, in which the government of Colombia stated that ‘it does not contest the sovereignty of the United States of Venezuela over the Archipelago of Los Monjes and, consequently, that it does not contest or have any complaint to make concerning the exercise of the sovereignty itself or of any act of ownership by that country over the said archipelago’; See Fifth Report on Unilateral Acts of States, above n 14, [26].

[56] These two concepts are largely indistinguishable, and the difference is largely a matter of usage, custom and convenience. See Jennings and Watts, above n 25, 1195 §580.

[57] Sixth Report on Unilateral Acts of States, above n 14, [21].

[58] (Cambodia v Thailand) (Merits) [1962] ICJ Rep 6, 23. See also Affaire des Frontières Colombo-Vénézueliennes (1922) 1 UNRIAA 223.

[59] Degan, above n 27, 293-303.

[60] Statement by Mr Brownlie, ILC 55th Session, Plenary Meeting of Thursday 10th July, 2003.

[61] Replies of Governments to the Questionnaire, above n 10, Reply from the Government of Norway.

[62] Anzilotti, above n 28, 335.

[63] Suy, above n 25, 17.

[64] Anzilotti, above n 28, 336-38; Suy, above n 25, 18; M Virally, La Pensée Juridique (1960) 92.

[65] Anzilotti, above n 28, 338-39; Degan, above n 27, 259.

[66] Anzilotti, above n 28, 339; see also Suy, above n 25, 19-21; Virally, above n 64 92.

[67] Anzilotti, above n 28, 339; Fiedler, above n 24, 1021; K Skubiszewski, ‘Les Actes Unilatéraux des Etats’ in Mohammed Bedjaoui (ed), I Droit International – Bilan et Perspectives (1991) 230, 242-44.

[68] Anzilotti, above n 28, 339; above n 25, 22-23.

[69] Anzilotti, above n 28, 345.

[70] Degan, above n 27, 260.

[71] Schwarzenberger, above n 50, 554; Rubin, above n 25, 26-27; Franck, above n 12, 616; Nuclear Tests Cases, [43].

[72] A Gigante, ‘Unilateral State Acts’ (1969) 2 New York University Journal of International Law and Politics 333, 335.

[73] See above n 24 and accompanying text.

[74] (23 May 1969) 1155 UNTS 331.

[75] See eg Official Records of the General Assembly, Suppl No 10, 51st Session, 343, UN Doc A/51/10, Addend 3, (1996); Replies of Governments to the Questionnaire, above n 10, Replies from the Governments of Argentina, El Salvador, Georgia, Israel, the Netherlands and Sweden; Degan, above n 27, 286-87.

[76] Sicault, above n 43, 657.

[77] International Law Commission, Second Report on Unilateral Acts of States, 51st Session, [77],UN Doc A/CN.4/500/Add1 (1999).

[78] P Cahier, ‘Le Comportement des États Comme Source de Droits et d’Obligations’ (1968) Recueil d’Études de Droit International en Hommage à Paul Guggenheim 237, 242.

[79] Replies from Governments to the Questionnaire, above n 10, Replies from the Governments of inter alia Argentina, Finland, Italy, Austria, Sweden.

[80] Application of the Convention on the Prevention and Punishment of the Crime of Genocide (prelim objections) (Judgment) [1996] ICJ Rep 622; Eastern Greenland Case; Nuclear Tests Cases [1974] ICJ Rep 253 [49].

[81] Replies from Governments to the Questionnaire, above n 10, Reply from the Government of Argentina.

[82] Skubiszewski, above n 67, 243.

[83] These articles relate to subsequent confirmation of an act (art 8), provisions of internal law regarding competence to conclude treaties (art 46) and specific restrictions on authority to express consent (art 47).

[84] Anzilotti, above n 28, 340.

[85] Art 53, VCLT.

[86] Manila Declaration on the Peaceful Settlements of Disputes GA Res 32/10, UN GAOR, 68th mtg, UN Doc A/Res/37/10 (1982).

[87] J P Jacqué, Eléments pour une Théorie de L’Acte Juridique en Droit International Public (1972) 161-62.

[88] Reuter, above n 30, 546.

[89] See the Statement by the Representative of Poland, UN Doc A/C.6/54/SR.25 (1999).

[90] Sicault, above n 43, 664.

[91] Fitzmaurice, above n 25, 230.

[92] Nuclear Tests Cases [1974] ICJ Rep 253, [43].

[93] M Koskenniemi, From Apology to Utopia: The Structure of International Legal Argument (1989) 307.

[94] Nuclear Tests Cases [1974] ICJ Rep 253, [43].

[95] Koskenniemi, above n 93, 308.

[96] Art 31(1).

[97] Sicault, above n 43, 648.

[98] [1974] ICJ Rep 253, [46].

[99] R Kolb, La Bonne foi en Droit International Public (2000) 336.

[100] See the discussion by Franck, above n 12, 617.

[101] Nuclear Tests Cases [1974] ICJ Rep 253 [43].

[102] Art 31.

[103] Eg the Note accompanying the Declaration on the Suez Canal, sent by the representative of Egypt to the Secretary-General of the UN on the 24 April 1957; Fourth Report on Unilateral Acts of States, above n 14, [141].

[104] Advisory Opinion Concerning the Status of Eastern Carelia [1923] PCIJ Ser B, No 5, 28 [hereinafter Eastern Carelia].

[105] Rights of Minorities in Upper Silesia (Minority Schools) [1928] PCIJ ser A No 15, 25 [hereinafter Minority Schools].

[106] [1986] ICJ Rep 574, [40].

[107] Verzjil, above n 46, 109.

[108] [1974] ICJ Rep 267, [43].

[109] [1986] ICJ Rep 132, [261].

[110] Jacqué, above n 87, 127.

[111] Gigante, above n 72, 337.

[112] [1974] ICJ Rep 253, [44].

[113] These articles relate to Error (art 48), Fraud (art 49), Corruption (art 50) and Coercion (arts 51 and 52).

[114] Dispute concerning the course of the Frontier between B.P. 62 and Mount Fitzroy (Argentina/Chile), Arbitral Award of 21 October 1994, RGDIP, 1996, vol 2, 552.

[115] [1974] ICJ Rep 253, [45].

[116] Suy, above n 25, 132; C. Rousseau, I Droit International Public (1970) 425-26; Degan, above n 27, 297; Fiedler, above n 24, 1021.

[117] Case Concerning the Temple at Prear Vihear (Cambodia v Thailand) (Merits) [1962] ICJ Rep 6, 23.

[118] Reuter, above n 30, 581.

[119] [1974] ICJ Rep 253, [43].

[120] Sicault, above n 43, 671.

[121] Skubiszewski, above n 67, [53].

[122] Gigante, above n 72, 341.

[123] Ibid 342.

[124] [1974] ICJ Rep 253, [46].

[125] Kiss, ‘Les Actes Unilatéraux dans la Pratique Francaise du Droit International’ (1961) 65 Revue Générale de Droit International Public 317.

[126] Ibid 321.

[127] R Quadri, ‘Cours Général de Droit International Public’ (1964 III) 113 Recueil des Cours de l’Académie de la Haye 237, 370.

[128] Kolb, above n 99, 325.

[129] S Carbone, ‘Promise in International Law: A Confirmation of its Binding Force’ (1975) 2 Italian Yearbook of International Law 166, 167.

[130] Quadri, above n 127, 364.

[131] (Minority Schools) [1928] PCIJ Ser A, No 15, 25.

[132] J L Brierly, ‘Law of Treaties’ [1950] 2 Yearbook of the International Law Commission 222, 227.

[133] Anzilotti, above n 28, 344.

[134] Gigante, above n 72, 342.

[135] Rubin, above n 25, 11.

[136] [1974] ICJ Rep 253, [43].

[137] J P Jacqué, ‘A propos de la promesse unilatérale’ in Mélanges offerts à Paul Reuter – Le Droit International: Unité et diversité, 327, 334. See the definition of an autonomous unilateral act, above n 27 et seq.

[138] Gigante, above n 72, 344.

[139] Rubin, above n 25, 23.

[140] International Law Commission, Fifth Report on the Law of Treaties, [1960] 2 Yearbook of the International Law Commission, art 22, 81.

[141] Ibid 105 [92].

[142] Schwarzenberger, above n 50, 553.

[143] Jacqué, above n 137, 335.

[144] I C MacGibbon, ‘Estoppel in International Law’ (1958) 7 International and Comparative Law Quarterly 468; Gigante, above n 72, 347.

[145] Ibid 351.

[146] MacGibbon, above n 144, 477.

[147] Rubin, above n 25, 21.

[148] Venturini, above n 36, 372.

[149] (Cambodia v Thailand) (Merits) [1962] ICJ Rep 6.

[150] Ibid Separate Opinion of Judge Alfaro, 40-42.

[151] (Honduras v Nicaragua) [1960] ICJ Rep 192.

[152] Separate Opinion of Judge Spender, 219-20.

[153] (Russia v Turkey) Hague Court Reports (Scott) 297 (Permanent Court of Arbitration, 1912).

[154] Ibid 322-23.

[155] Lord McNair, The Law of Treaties (1961) 487.

[156] Gigante, above n 72, 353.

[157] Ibid.

[158] MacGibbon, above n 144, 512; Temple Case (Separate Opinion of Judge Alfaro) 40; Gigante, above n 72, 349.

[159] Jacqué, above n 137, 339.

[160] M Lachs, ‘Some Thoughts on the Role of Good Faith in International Law’ in R J Akkerman, P J van Krieken and C O Pannenborg (eds), Declarations on Principles: A Quest for Universal Peace (1977) 48.

[161] [1923] Ser A No 1, 25.

[162] Charpentier, above n 6, 375.

[163] Ibid 375-76.

[164] Ibid 374.

[165] See above text accompanying n 99 et seq.

[166] Lachs, above n 160, 48.

[167] J F O’Connor, Good Faith in International Law (1991) 6.

[168] Lachs, above n 160, 49.

[169] M Lachs, ‘General Course in Public International Law’ (1980 IV) 169 Recueil des Cours 198.

[170] See the statement of Lachs in this regard, ibid 50-51.

[171] Kolb, above n 99, 91-92.

[172] M De Taube, ‘L’inviolabilité des traités’ (1930 II) Recueil des Cours 295.

[173] J Kunz, ‘The Meaning and Range of the Norm Pacta Sunt Servanda’ (1945) 39 American Journal of International Law 180, 197.

[174] Ibid.

[175] Kolb, above n 99, 97-98.

[176] Ibid 88-89; J F. O’Connor, above n 167, 122.

[177] Lachs, above n 169, 193; Suy, above n 25, 45; M Lachs, ‘Pacta Sunt Servanda’ in (2000) III Encyclopedia of Public International Law 852.

[178] Suy, above n 25, 271.

[179] Above n 59 and accompanying text and seq.

[180] See the discussion in Part II relating to conditions of validity.

[181] Carbone, above n 129, 167; Quadri, above n 127, 364; Kolb, above n 99, 333.

[182] First Report on Unilateral Acts of States, above n 14, [157].

[183] See the discussion of this in Part II.

[184] Fifth Report on Unilateral Acts of States, above n 14, Add1 [137].

[185] See arts 53, 61 and 62, Vienna Convention on the Law of Treaties (23 May 1969) 1155 UNTS 331.

[186] See arts 27, 28 and 29, Vienna Convention on the Law of Treaties (23 May 1969) 1155 UNTS 331.

[187] See inter alia, Rubin, above n 25, 27-28; R S J McDonald and B Hough, ‘The Nuclear Tests Cases Revisited’ (1977) 20 German Yearbook of International Law 337, 353; P Lellouche, ‘The International Court of Justice – The Nuclear Tests Cases: Judicial Silence v Atomic Blasts’ (1975) 16 Harvard International Law Journal 614, 625.

[188] [1974] ICJ Rep 253, [51].

[189] Note dated 10 July 1974, from the French Embassy in New Zealand to the New Zealand Ministry of Foreign Affairs. Similar statements were made by the Office of the President of France, by the President himself in a press conference, in a television interview and a press conference by the Minister of Defence, and before the UN General Assembly by the Minister for Foreign Affairs. The reference to ‘normal course of events’ was not repeated in the later statements.

[190] Lellouche, above n 187, 625; McDonald and Hough, above n 187, 353.

[191] D Khosla, ‘Nuclear Test Cases’ (1978) 18 Indian Journal of International Law 322, 332.

[192] MacDonald and Hough, above n 187, 353; Dissenting Opinion of Barwick J, [1974] ICJ Rep, 449.

[193] Khosla, above n 191, 333-34.

[194] Franck, above n 12, 612.

[195] Replies of Governments to the Questionnaire, Replies of Governments to the Questionnaire, above n 10, Replies from the Governments of Austria, The Netherlands, El Salvador seem to indicate acceptance of the development of ‘rules’ applicable to unilateral acts.

[196] Ibid Reply from the Government of the United Kingdom.

[197] Ibid Replies from the Government of Luxembourg, Finland.

[198] Report on the International Law Commission on the work of its 48th Session. GA Res 160, 51st sess, UN Doc A/RES/51/160 (1997).

[199] Yearbook of the International Law Commission (1997). UN Doc A/CN.4/SER.A/1997.Add l (Part 2) [196].

[200] International Law Commission, Ninth Report on Unilateral Acts of States, 58th Session UN Doc A/CN.4/569 (2006).

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