- P P - 9. - W - - NORTHERN IRELAND (9 Territorial Sea Act 1987* [Entry into force: 1 Cctober 19871 [Criginal: English] 1987 Chapter 49 Pn Act to provide for the extent of the territorial sea adjacent to the British Islands. (15 Xay 19871 ae it enacted by the Queen's Most Excellent Majesty, by and with the advice and consent of the Lords Spiritual and Temporal, and Commons, in this present Parliament assembled, and by the authority of the same, as foilows: Extension of territorial sea 1. (1) Subject to the provisions of this Act: (a) the breadth of the territorial sea adjacent to the United Kingdom shall for all purposes be 12 nautical miles; and (b) the baselines from which the breadth of that territorial sea is to be measured shall for all purposes be those established by Her Majesty by Order in Council. (2) Her Yijesty may, for the purpose of implementing any international agreement or otherwise, Sy Order in Council provide that any part of the territorial sea adjacent to the Un...