Immigration Act 1971

26 (1) The owners or agents of a ship or aircraft employed to carry passengers for reward shall not, without the approval of the Secretary of State, arrange for the ship or aircraft to call at a port in the United Kingdom other than a port of entry for the purpose of disembarking passengers, if any of the passengers on board may not enter the United Kingdom without leave and have not been given leave, or for the purpose of embarking passengers unless the owners or agents have reasonable cause to believe all of them to be patrial.

(2) The Secretary of State may from time to time give written notice to the owners or agents of any ships or aircraft designating control areas for the embarkation or disembarkation of passengers in any port in the United Kingdom, and specifying the conditions and restrictions (if any) to be observed in any control area ; and where by notice given to any owners or agents a control area is for the time being designated for the embarkation or disembarkation of passengers at any port, the owners or agents shall take all reasonable steps to secure that, in the case of their ships or aircraft, passengers do not embark or disembark, as the case may be, at the port outside the control area and that any conditions or restrictions notified to them are observed.

(3) The Secretary of State may also from time to time give to any persons concerned with the management of a port in the United Kingdom written notice designating control areas in the port and specifying conditions or restrictions to be observed in any control area; and any such person shall take all reasonable steps to secure that any conditions or restrictions as notified to him are observed.