The Concept of Special Custom in International Law

There are regrettably few cases in international law that go into the question of the proof necessary to establish a customary rule binding upon the defendant state. And from those few cases, notably those decided by the World Court, most writers have drawn pessimistic conclusions as to the proof needed for custom because of the Court's apparent insistence, in Professor Falk's words, upon “some tangible evidence of consent on the part of the state that is bound”. FN1 A showing of consent is a very difficult proposition. Many legal disputes arise precisely because neither side has previously consented to the same rule. As Lauterpacht argued, to say that prior consent must be shown in order to reach a legal conclusion in any given international dispute is tantamount to rejecting the possibility of the existence of the vast majority of the rules of international law. FN2 But then, how can we explain the World Court's reasoning in the Asylum, Right of Passage, and Fisheries Cases FN3 in which the element of consent on the part of the defendant states seemed to play such a vital role in the Court's reasoning concerning the existence of binding rules of law? FN4 . The purpose of this essay is to argue that the widely accepted view of the World Court's jurisprudence as emphasizing the requirement of a [page 212] showing of consent is a mistaken view, not because scholars have misread the cases but rather because of a widespread failure to draw a basic distinction between special (or ‘local’, or ‘particular') customary international law and general customary international law. The cases just cited, which shall be examined shortly, dealt with special, not general, custom. The stringent requirements of proof of consent in these cases thus do not apply to the large body of general norms of international law binding upon all states, but rather apply only in similar cases of ‘special’ custom.