(1) The provision that may be made by virtue of section 17(2) (enforcement of prohibitions or requirements) includes provision as to the powers and duties of prescribed persons in relation to -
(a) British ships in foreign waters or international waters,
(b) ships without nationality in international waters, and
(c) foreign ships in international waters.
(2) Regulations may make provision by virtue of this section only for the purpose of enforcing relevant prohibitions or requirements.
(3) A prohibition or requirement is a "relevant prohibition or requirement" for the purposes of this section if it is -
(a) a prohibition or requirement specified by the regulations which is imposed by regulations for a purpose mentioned in any of paragraphs 2 to 7, 15(a), (b) or (c) or 16(a) of Schedule 1, or
(b) a prohibition or requirement imposed by a condition of a licence or direction issued by virtue of section 15 in relation to a prohibition or requirement mentioned in paragraph (a).
(4) The powe
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