Academic journal article Duke Journal of Comparative & International Law

Custom at the Heart of International Law

Academic journal article Duke Journal of Comparative & International Law

Custom at the Heart of International Law

Article excerpt

From: Melanges offerts a Paul Reuter (Paris: Pedone, 1981) 479-99.

By way of custom "that which `is' becomes that which `must be'."

This lapidarian formula, used by Judge Armand Ugon in his individual opinion in the Rights of Passage Case,(1) raises endless questions for all those who are preoccupied by the fundamental question of the relationship between fact and law.

That customary rules exist in the international legal system is not contested. Phrased differently, it cannot be denied that certain international practices, when they display certain characteristics, are considered in international law to create or manifest norms, the content of which is precisely such as to render these practices obligatory.

It is not contested either that custom enjoys privileged status in the international order: "custom is even more central than the treaty,"(2) according to the terms used by Professor Reuter.

Moreover, it is established that if an agreement can easily be reached on the existence in international law of customary rules, the analysis of these rules almost invariably leads to anguished inquiries as to the "foundation" of law and lively doctrinal controversies: it is clear that custom disturbs.

Why, one can therefore ask, does the problem of custom stir such passions?

It is, we think, because the obligatory character of custom--defined as a certain state of fact considered to be law--raises, in an isolated case, the same type of question as is raised by the obligatory character of the entire legal order on a global scale, since what is a legal system after all, if not a certain order of fact considered to be law?

The characterization of the state of fact which can give birth to custom, and the order of fact which can constitute a legal order, seem to confirm this analogy.

In both cases, the fact must have achieved a sufficient density to manifest "at least a provisional stabilization of the interests present."(3)

More precisely, the state of fact which can give birth to the customary rule must result from a repetition of practice; phrased differently, it is the effectiveness of a certain behavior which is determinative.

Similarly, the order of fact which can be considered as a legal order must be composed of norms which are, according to Kelsen's well-known expression, "largely and generally applied and observed"(4): the criterion here is therefore also the effectiveness of certain kinds of behavior.

In other terms, custom plays a role in unveiling--in laying bare--the legal system. It is so troubling because it constantly gives rise to the question of the origin of obligation in a legal system which fairly easily disregards the essential question of the foundation of its obligatory character, which is impossible to resolve on a strictly legal basis, in favor of the existential question of the foundation of the obligatory character of its different norms, which can be resolved in a very reassuring way within the framework of its formalistic structure.(5)

Custom therefore raises the problem of the original creation of law and not that of the production of law by the legal system. Due to its autonomous emergence in the fine arrangement of law, custom provokes again the initial question which was masked by the same arrangement: that of the appearance, which is also autonomous, that is to say, not capable by definition of depending on a pre-existing legal norm, of the legal order itself. And in this sense, an analysis of that which is international custom may perhaps allow us to bring certain elements into the eternal debate over the nature of the legal order.

But let us leave these few intuitions aside and see, before trying to verify them, how doctrine has treated the problem of the obligatory character of international custom, that is to say, of the existence of customary rules in international law. …

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