International Waterways - Straits

Some straits are more important than others because they are the sole connecting links between oceans and interior waters. For example, the Strait of Gibraltar gives access from the Atlantic Ocean to the Mediterranean and Aegean Seas. Other straits are not as important. The availability of alternate routes does not in itself deprive a strait of its character as an international waterway. In the Corfu Channel case, 1949 I.C.J. 4, 1949 WL 1 (I.C.J.), the INTERNATIONAL COURT OF JUSTICE rejected the test of essentiality as the only route, ruling that "the decisive criterion is rather [the strait's] geographic situation as connecting two parts of the high seas and the fact of its being used for international navigation."

The 1958 GENEVA CONVENTION on the Territorial Sea and Contiguous Zone (516 U.N.T.S. 205, 15 U.S.T. 1606, T.I.A.S. No. 5639) does not deal comprehensively with international waterways, but does provide that "[t]here shall be no suspension of innocent passage of foreign ships through straits which are used for international navigation between one part of the high seas and another part of the high seas or the territorial sea of a foreign state" (art. 16, § 4). A territorial sea is the water that comes under the sovereign control of a state.

A coastal state has somewhat greater control of innocent passage through its territorial seas than of innocent passage through a strait joining two areas of high seas. Passage may be suspended through TERRITORIAL WATERS when essential for security. This means that warships are free to pass through straits but may be denied access to territorial seas.

Since the 1960s a great majority of coastal states have extended their claims on territorial seas from three miles to 12 miles from the low-water mark, some even farther. This change has been a matter of concern to the U.S. government, as a 12-mile limit converts 121 straits to territorial seas, some of which have strategic military importance.