C. The creation of customary law

So far this chapter has dealt almost exclusively with international legislation through the multilateral treaty-making process, which indeed is the principal method of manufacturing new international law.

However, as already mentioned in the introduction, customary law is the other main source of rights and obligations under international law and therefore cannot be entirely neglected in the present context. This is especially so because customary, unlike conventional, law generally applies to all states (except those that have always and consistently excluded themselves from the practice in question) and not only to the parties to a particular instrument.

At first sight, it seems oxymoronic to suggest that customary law which is derived inductively from the practice of states insofar as such practice is motivated by a sense of legal obligation - can be "legislated" in the usual sense of that term. And, of course there is no straightforward way of doing so, comparable to the treaty route, which though long and tortuous, can be seen as proceeding step by step from the proposal to initiate to the entry into force of a multilateral law-making treaty.

Nevertheless, customary law can be somewhat shaped and directed, because the practices of states can be consciously affected by various international actions, particularly by significant IGOs. Many of the hundreds of resolutions that are adopted each year by international organs are addressed to states and recommend that they act in particular ways and may even suggest that they are legally obliged to do so - obviously in the hope, if not the firm expectation, that some or many will conform their conduct as a result of these importunings.

Although most such recommendations are expressed in ordinary resolutions and deal with issues of lesser or transitory moment, some are deliberately framed as solemn or universal declarations and adopted with ceremony by a senior organ, such as the United Nations General Assembly. The expectation that states will make a real effort to conform their conduct to such texts appears from their preambles or from the adopting resolutions, and sometimes also from later inquiries, usually solicited by the adopting organ and addressed to the executive head of the IGO, as to how states have actually responded to the declaration.

The formulation of such a declaration is often subject to essentially the same procedures as described in respect of multilateral treaties, involving consideration by expert and representative organs, consultations with governments and with NGOs, and adoption in a plenary organ by a high majority or by consensus.⁴⁷ Indeed sometimes when this process is started it may not be clear whether the final product will be a declaration or a treaty, and the choice between these two may only be made at a relatively advanced stage of the process that is, when it can be determined if at that stage a sufficient number of states is prepared to enter into a binding treaty. But, whether or not a declaration is originally adopted only as a second-best solution, it may then serve as the forerunner of a later treaty, in that the groundwork is laid and the general legal principle is established by the former instrument, while the later treaty covers the same lines, though in greater detail and with more precision.

Solemn legislative declarations⁴⁸ can thus contribute to the international legislative process in two entirely separate ways. They may be precursive to and guide a later treaty-making process, in which reference is often made to the general legal principle already stated in the declarations.⁴⁹ And they are also and perhaps primarily designed to influence the conduct of states directly -and to the extent that they are successful in doing so international customary law may be created. In effect they may catalyse the creation of customary law by expressing in normative terms certain principles whose general acceptance is already in the air (for otherwise their adoption by an IGO organ would not receive the necessary support) and thereby making it easier and more likely for states to conform their conduct to them.

There is yet another and in a sense more circuitous way in which the creation of new customary law can be furthered through deliberate international action: i.e. through the adoption of multilateral lawmaking treaties. Though of course these instruments primarily create rights and obligations only for their parties and thereby influence their conduct, to the extent that such conduct then becomes the international standard, even states that for some reason have not become parties to the treaty may feel obliged to conform their conduct to some or all of the treaty provisions.⁵⁰ Thus the process of creating new law-making treaties may, as a by-product, also facilitate the creation of new customary law.

This having been said, it must also be admitted that so far there are few clear instances of customary environmental legal principles. This is largely so because environmental law itself is of relatively recent vintage, and thus there has been little time for consistent state practice to develop, either in response to solemn declarations by IGOs or through the general acceptance of norms set out in multilateral treaties.⁵¹ However, the processes described above have in other areas, and in particular that of human rights, been notably productive in the creation of customary law, and there is therefore every reason to expect that the same will apply in respect of environmental principles.