This part applies if an authorised officer or police officer—
(a) lawfully enters a place in the course of performing a function or exercising a power under chapter 2 , including, for example—(i) under section 16 or 18 in investigating an allegation of harm, or risk of harm, to a child; or(ii) under an assessment order in investigating whether a child is a child in need of protection; or
(b) enters a place under a warrant for apprehension of a child who, under section 164 , has been unlawfully removed from a person’s custody or guardianship.Note—A warrant for apprehension of a child may be issued under part 3 .