Base Lines

in international law, the lines from which the breadth of the territorial sea is measured outward toward the sea. They are sometimes known as initial lines (in Russian, iskhodnye linii). In international practice there are two ways of measuring the breadth of territorial waters: from the low-water line when the coast has an even outline and from imaginary straight lines joining protruding points along the coast if the coastline is deeply indented and cut into or if there is a chain of islands near the coast. There are no rules limiting the length of base lines; however, the drawing of the lines must not depart to any appreciable extent from the general direction of the coast. Base lines may be drawn to rocks covered at the high tide when lighthouses or installations permanently above sea level have been erected on them. At the entrance to bays the coasts of which belong to a single state, the base lines (“closing lines”) are drawn as follows. If the width of the entrance does not exceed 24 nautical miles (44.4 km), the closing line is drawn between the opposite points of the natural entrance to the bay. If, on the other hand, the width of the bay exceeds 24 nautical miles, the base lines are drawn inside the bay in such a manner that a 24-mile segment of a straight line will enclose the maximum possible area of water. These provisions do not apply to so-called historic bays (for example, the Bay of Biscay), the width of whose entrances may considerably exceed 24 nautical miles, or in cases where the base line system is applied to the entire coastline because it is indented. Coastal states must indicate base lines on the sea charts they publish.

Waters on the landward side of the base line form part of the internal waters of the state.

Since the decision of the United Nations International Court of Justice on the Anglo-Norwegian dispute in 1951 and more particularly since the adoption of the Geneva Convention on the Territorial Sea and Contiguous Zone in 1958, which fully regulated questions connected with the base line, the method of measuring the breadth of territorial waters on the basis of the base line may now be regarded as generally accepted in international law.