ABSTRACT
This chapter outlines the progressive sequence of Irish offshore jurisdictional claims and considers the implications of counterclaims by adjacent states to areas also claimed by Ireland, paying particular attention to the question of boundary demarcation between Ireland and the United Kingdom. The evolution of the offshore jurisdictional claims of the Republic of Ireland beyond the limits of the territorial sea coincides with the extension of hydrocarbon exploitation into deeper water areas. In 1970, the Irish government extended its jurisdiction off the west coast to an area roughly coincident with the 200 metre isobath, thus incorporating the Slyne Trough and Donegal Basin within its sphere of control. While the 200 metre isobath had originally been used by the United States to define its continental shelf, in the Irish case the shelf extends well beyond this limit over a large area. Thus, early in 1974, the Irish government made a further designation extending approximately to the base of the continental slope.
