If, in contravention of this Act or the regulations--
(a) an employee or agent of a licensee, or
(b) an employee or agent of the manager of licensed premises, or
(c) a person acting, or purporting to act, on behalf of a licensee or the manager of licensed premises,sells or supplies liquor on the licensed premises, the licensee or manager (as the case requires) is guilty of an offence and liable to the punishment specified for the contravention.