Manifest Intent and the Generation by Treaty of Customary Rules of International Law

I shall argue in this essay that the World Court used a method which might be called the rule of manifest intent in the North Sea Continental Shelf Cases, that this method differs from a more traditional approach found in the writings of publicists, and that this new method accords well with the growing need to objectify and place upon a scientific basis the methodology by which one may determine what in fact are the rules of customary law. Tags: Customary International Law, Norm-creation by Treaty, Manifest Intent Rule, Continental Shelf Convention, North Sea Continental Shelf Cases, Equidistance Principle [pg892]** The World Court's recent decision in the North Sea Continental Shelf Cases FN1 is a major contribution to that branch of the theory of customary international law dealing with norm-creation by means of a treaty. The Court articulated a new methodology for determining which provisions in treaties can form the basis of universally binding customary law. As the spreading network of international conventions becomes more fine-meshed, the substantive rules of international customary law may be expected to conform more and more closely to the provisions in these conventions. The World Court has implicitly recognized this process in many prior opinions, but it was not until the Continental Shelf decision that the link between treaty and custom was focused upon with precision. I shall argue in this essay that the Court used a method which might be called the rule of manifest intent, that this method differs from a more traditional approach found in the writings of publicists, and that this new method accords well with the growing need to objectify and place upon a scientific basis the methodology by which one may determine what in fact are the rules of customary law. I. THE BASIS FOR THE CONTINENTAL SHELF DECISION Courts do not announce methodological procedures in a vacuum; rather, a specific decision is the agency which gives life and shape to methods of legal analysis. The North Sea Continental Shelf Cases presented a very special kind of problem which perforce colored the Court's analytical methods. At the heart of the dispute was whether the concept of equidistanceFN2 is internationally required as determining the legal shares in the North Sea of the adjacent coastal states, Denmark, Federal Republic of Germany, and The Netherlands. This concept was given expression in Article 6, paragraph 2, of the 1958 Geneva Convention on the Continental Shelf,FN3 a multilateral convention among 39 states, including Denmark and The Netherlands but not including the Federal Republic, which disputes the equidistance concept.FN4 As the Court immediately pointed out, an equidistance line between two adjacent states extending into a body of water [pg893] divides the water roughly equally for the states so long as their coastlines are straight or nearly straight. But where one coastline is concave or recessing, then an equidistance line between the concave state and the straight state would disproportionately favor the latter, cutting off the former's access to the body of water and the subjacent seabed.FN5 Since the Federal Republic's coast is concave to both the adjacent states—Denmark and The Netherlands—an equidistance line would meet at the apex of a triangle at a relatively short distance from the Federal Republics coast, "cutting off” any further areas of the continental shelf beyond this triangle.FN6 But this method as applied to Germany would, in the Court's words, produce “results that appear on the face of them to be