Customary international law lacks the certainty and stability needed for military and commercial activities

There is at least a germ of truth in this argument. The United States and its maritime activities are functioning reasonably well under the customary regime of the law of the sea. Most of the Convention is indeed a codification of customary international law. President Reagan's 1982 statements acknowledged this and pledged that the United States would abide by its rules.⁴¹ But customary law does not provide the precision and detail of a written document. It may establish a principle, but its content may remain imprecise, subject to a range of interpretations. With respect to the exclusive economic zone (EEZ), for example, it is generally conceded today that the principle of the zone has become a part of customary international law. But what about its content? The details are contained in a set of articles codifying a series of compromises worked out in meticulous detail in the negotiations leading up to the signing of the Convention. The rules for determining the allowable catch of the living resources of the EEZ, the determination of the coastal State's capacity to harvest them, the determination of the allowable catch by other States and the rules governing the coastal State's establishing of terms and conditions for foreign fishermen in their EEZs are laid out in detail.⁴²

Customary rules are fuzzy around the edges and may not be recognized as binding by an opposing State. The "jurisdiction creep," which continued after the 1958 and 1960 First and Second UN Conferences on the Law of the Sea, illustrated the futility of relying on customary law to protect our vital security interests. Only a written document can provide the certainty and stability required by our governmental agencies and private maritime enterprises. And in any dispute with a foreign State to secure its compliance with the rules set forth in the Convention, arguments based on a written agreement rather than an asserted principle of customary international law would be much more effective.