(1)The powers conferred on an enforcement officer by Schedule 3 to this Act shall be exercisable in relation to any ship to which section 18 or 19 above applies for the purpose of detecting and the taking of appropriate action in respect of the offences mentioned in those sections.
(2)Those powers shall not be exercised outside the landward limits of the territorial sea of the United Kingdom in relation to a ship registered in a Convention state except with the authority of the Secretary of State; and he shall not give his authority unless that state has in relation to that ship—
(a)requested the assistance of the United Kingdom for the purpose mentioned in subsection (1) above; or
(b)authorised the United Kingdom to act for that purpose.
(3)In giving his authority pursuant to a request or authorisation from a Convention state the Secretary of State shall impose such conditions or limitations on the exercise of the powers as may be necessary to give effect to any conditions or limitations imposed by that state.
(4)The Secretary of State may, either of his own motion or in response to a request from a Convention state, authorise a Convention state to exercise, in relation to a British ship, powers corresponding to those conferred on enforcement officers by Schedule 3 to this Act but subject to such conditions or limitations, if any, as he may impose.
(5)Subsection (4) above is without prejudice to any agreement made, or which may be made, on behalf of the United Kingdom whereby the United Kingdom undertakes not to object to the exercise by any other state in relation to a British ship of powers corresponding to those conferred by that Schedule.
(6)The powers conferred by that Schedule shall not be exercised in the territorial sea of any state other than the United Kingdom without the authority of the Secretary of State and he shall not give his authority unless that state has consented to the exercise of those powers.