As was noted in the Introduction, scholars advocating the notion of an environmental non-regression principle usually seek to ground it as some kind of international legal norm. The classical starting point for the assessment of whether a purportedly novel international norm has emerged, is the international ‘canon’ of the sources of international law, which is usually considered to be expressed by Article 38 ICJ Statute. To be certain, there has been a recurrent debate as to whether the doctrinal focus on the traditional canon of international legal sources is (still) adequate. The above discussion of soft law documents has further highlighted that the differentiation between formally binding law, ‘soft’ law, and non-binding statements is far from straightforward. Nonetheless, where the emergence of a norm is discussed that allegedly transcends the confines of a specific treaty, it still appears to be widely agreed that such a norm would either have to be established as a norm of customary international law (by virtue of relevant state practice and opinio juris) or a general principle of international law (by virtue of a widespread occurrence in domestic legal systems or in the international legal system itself). The following discussion starts from this classical position and hence seeks to provide a cautious answer as to whether an environmental non-regression principle may be considered part of international custom (Section I.) or the general principles of international law (Section II.). It will be seen that in the current state of the law, non-regression should be considered part of international environmental soft law (Section III.).

CUSTOMARY INTERNATIONAL LAW

In principle, there seems to be general acceptance that customary law is, and remains to be, a valid source of international law. International custom has, however, remained highly contentious when it comes to the specifics of how to detect the two constituent objective and subjective elements of (state) practice and opinio juris (sive necessitatis). While these two requirements seem to be widely agreed in principle, their sufficiency and operation are controversial. It was already noted above that the ICJ also indicated an additional third criterion, namely the ‘fundamentally norm-creating character’ of the suggested norm. Furthermore, commentators have regularly pointed to the inherent problems of the relationship between the objective and subjective elements, and paid considerable attention to the apparent shift from ‘inductive’ to ‘deductive’ methods in the ascertainment of customary law.