Codification

As pointed out above, most members of the international community tend to prefer treaties to custom, for the former are more certain and result from the willing participation of contracting parties in the negotiating process. Between the 1960s and the 1980s this natural preference for treaties became more pronounced, because new States began actively to participate in international relations and insisted that the old law be changed so as to take account of their needs and concerns. The 'old' States considered it advisable to update the law by a treaty-making process, so as to be in a position actively to discuss and negotiate the adaptation of the law to new realities. This process is called 'codification'.

Codification treaties may have the following effects.

1. A declaratory effect, that is they simply codify or restate an existing customary rule.

2. A crystallizing effect, in that they bring to maturity an emerging customary rule, that is a rule that was still in the formative stage.

3. A generating effect, which materializes whenever a treaty provision creating new law sets in motion a process whereby it gradually brings about, or contributes to, the formation of a corresponding customary rule.

The introduction of jus cogens in the 1960s the emergence of jus cogens.

In the late 1960s there occurred an upgrading of certain fundamental rules produced by traditional sources of law, with the introduction of jus cogens, as a result of the endeavours of the socialist and developing countries. These countries claimed that certain norms governing relations between States should be given a higher status and rank than ordinary rules deriving from treaties and custom. Consequently, treaties must not deviate from those supreme norms and, if they did, were to be regarded as null and void. According to the proponents of this view, the norms in question covered self-determination of people, the prohibition of aggression, genocide, slavery, racial discrimination, and, in particular, racial segregation or apartheid.

Jus cogens was accepted but on condition that any State invoking it be prepared to submit its determination to the ICJ. The Vienna Conventions on the Law of Treaties of 1969 and 1986 provided, in Article 53, as follows:

‘A treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law. For the purposes of the present Convention, a peremptory norm of general international law is a norm accepted and recognized by the international community of States as a whole as 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.’

Clearly, a peremptory norm can оnly take shape if the most important and representative States from the various areas of the world consent to it. However, it is difficult for a State, whether or not it is a Great Power, to oppose the formation of a peremptory norm: numerous political, diplomatic, or psychological factors dissuade States from assuming a hostile attitude towards emerging values which most other States consider to be fundamental.

The provisions of the Vienna Convention on peremptory norms suffer from a major limitation: they may only be invoked by a State that is both party to the Vienna Convention and party to the bilateral or multilateral treaty it intends to have declared contrary to jus cogens.

The customary rule on jus cogens operates with regard to States that are not party to the Vienna Convention (but party to a treaty assertedly contraty to a peremptory rule).