排他的経済水域・大陸棚の境界画定に関する国際法理 : 東シナ海における日中間の対立をめぐって

The new international legal order of the ocean has been extensively embodied in the United Nations Convention on the Law of the Sea (UNCLOS), which was adopted at the Third U. N. Conference on the Law of the Sea in 1982 and became effective in 1994. The sovereign right and jurisdiction of a coastal state in its 200-mile exclusive economic zone (EEZ) and continental shelf has largely expanded under UNCLOS, As a result, many disputes on the maritime boundaries have occurred all over the world among states whose coasts are opposite or adjacent to each other. The East China Sea is not an isolated case. The dispute was provisionally settled between Japan and Korea by the Japan-Korea Continental Shelf (South) Agreement of 1974 with respect to the overlapping areas of their claims in the East China Sea, but no such agreement has been concluded between Japan and China in the same sea. It is provided in UNCLOS, to which both Japan and China are the parties, that the delimitation of the exclusive economic zone or continental shelf between States with opposite or adjacent coasts shall be effected by agreement on the basis of international law, as referred to in Article 38 of the Statute of the International Court of Justice, in order to achieve an equitable solution (Arts.74 and 83). Since this provision does not offer any clear legal basis for settling maritime boundary disputes, one must have recourse to international customary law and judicial judgments. Two principles of international law have been advocated for the delimitation of maritime boundaries: the equidistance principle and the equitable principle. Relying upon the former, China has claimed application of the natural prolongation theory of its land territory in order to extend its continental shelf up to the Okinawa Trough near the Okinawa Islands. On the other hand, Japan, supporting the latter principle, has consistently attempted to apply the median line, every point of which is equidistant from the nearest points on the baselines from which the breadth of the EEZ of each of the two States is measured. The conflict of the two States\u27 positions has not yet been solved. The judicial opinions of the International Court of Justice (ICJ), as shown in many cases concerning the delimitation of maritime boundaries, seem to indicate that the theory of natural prolongation has not played a decisive role in delimiting the overlapping continental shelves, thus gradually losing its relative importance as a legal principle, and that the use of the median line has instead gained relative weight. International law is, however, in the process of development in this respect, and some tentative arrangement for a joint development of the two States may well be conducive to the peaceful and effective use of the ocean area which is extremely precious for all states facing the South China Sea. Political prudence is strongly required for the governments concerned to get over the difficulties in drawing a concrete and satisfactory line