International Society—Consent and
Custom as Sources of Law
It was noted in Chapter 1 that international society is made up of a set of constitutive rules. These have been equated to what in international law are known as peremptory, jus cogens or general rules of international law. These are the rules that identify states as the members of international society, place nonnegotiable limitations on their actions and provide a baseline agreement on how other rules are formulated. This formulation finds expression in Article 53 of the Vienna Convention on the Law of Treaties. It defines the peremptory norm as that which is 'accepted and recognized by the international community of states as a whole'. It is 'a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character.'1 In this sense there is a duality to international law. At one level, law can be made by consenting states; at another deeper level, law can be made by the 'community of states as a whole'. States cannot object to the second type of law and must observe it when making their own contracts. What exactly passes for this second level of 'general international law' is a matter of dispute. Who exactly speaks for the 'community of states as a whole'? What is clear, however, is that the introduction of 'a new law-making procedure which does not require the consent of individual states for the emergence of peremptory rules… would obviously amount to a fundamental change in the constitutional principles of the international legal order relating
Such uncertainty does not mean that international society is non-existent, but it does mean that its constitutive rules are a matter of political dispute. Onuf's claim (see Chapter 1) that sovereign equality is jus cogens may be a good place to start. As this chapter demonstrates, however, the corollary of this, that international law can only bind states if they first consent to be so bound, is contested. Indeed, the argument for an alternative to this positivist
1 Vienna Convention on the Law of Treaties (1969) May 23, U.N. Doc. A/Conf. 39/27, at:
2 Gennady M. Danilenko, 'International Jus Cogens: Issues of Law-Making', European Journal
of International Law, 2 (1991), 47–8.