International Law - Antonio Cassese

Oxford University Press

First edition 2001 - p.86-113

Second edition 2005 – p.46-71

Unit 3.

International lawmaking: custom and treaties traditional law

From the beginning of the international community States have evolved two principal methods for creating legally binding rules: treaties and custom. Both were admirably suited to the exigencies of their creators. Both responded to the basic need of not imposing obligations on States that did not wish to be bound by them. No outside ‘legislator’ was tolerated: law was brought into being by the very States that were to be bound by it.

Treaties in particular, being applicable to the contracting parties only, perfectly reflected the individualism prevailing in the international community. Custom, although it gave rise to rules binding on all members of the community, also ultimately rested on consent.

The unfettered freedom of States was reflected in another feature of international lawmaking: the absence of any hierarchy between custom and treaties as sources of law. In other words, rules created by means of bilateral or multilateral treaties were not stronger than, or superior to, customary or 'general' rules, and vice versa. Both sets of rules possessed equal rank and status.

New trends

It should be noted, first, that the emergence in the twentieth century of a great number of States, many of them with different ideological, political, and cultural backgrounds (first the socialist countries and later developing States) meant that the international regulation of treaties had to become more certain, detailed, and consonant with the demands of these new States. As a result of the consequent need to codify, reshape, and develop traditional rules, States agreed to devote a whole treaty to the 'birth', 'life', and 'death' of international agreements.

Second, in recent years a set of fundamental values has emerged. States agree both on their content and on their crucial importance. By the same token, a new category of general international rules has come into being designed to enshrine those values: peremptory rules or jus cogens.

Jus cogens is hierarchically superior to all the other rules of international law; hence, the three general principles governing the relationship between international rules do not apply to them.

Third, as we shall see infra it is now, at the least, questionable whether States may object to the formation of a customary rule thereby remaining outside it. The international community is less anarchic and individualistic, and far more integrated than in the past. Consequently community pressure on individual States, including Great Powers, is such that it proves difficult for a State to avoid being bound by a new general rule.

CUSTOM

Custom is made up of two elements: general practice, or usus or diuturnitas, and the conviction that such practice reflects, or amounts to, law (opinio juris) or is required by social, economic, or political exigencies (opinio necessitatis).

The main feature of custom is that normally it is not a deliberate lawmaking process. As we shall see, in the case of treaties, States come together willingly to agree upon legal standards of behaviour acceptable to all those participating in the lawmaking process. Their main and conscious intent is to bring about those standards. In the case of custom, States, when participating in the norm-setting process, do not act for the primary purpose of laying down international rules. Their primary concern is to safeguard some economic, social, or political interests.

As pointed out above, a second feature differentiating custom from treaties is that customary rules are normally binding upon all members of the world community (or of a regional group of States, in the case of regional customs), whereas treaties only bind those States that ratify or adhere to them.