Sustainable development in international lawEssay on the legal implications of an evolutive norm

Sustainable development was elaborated essentially within the framework of the United Nations and has, since its consecration at the Rio Summit in 1992, widely penetrated both conventional and general international law. Sustainable development lays down a general objective for the international community to achieve, and requires, to this end, the integration of economic, social and environmental considerations. Its intrinsically evolutive nature means that it easily adapts to changing circumstances and to the diversity of situations it is intended to govern. Aimed at reconciling a priori opposing interests through their integration, one of the primary functions of sustainable development is to be found in the influence it exerts on the interpretative process. Its flexibility and malleability make it, in this context, a convenient legal tool granting the judge a significant margin of appreciation. Sustainable development’s evolutive nature can thus authorise a dynamic interpretation of norms; legitimise a balancing exercise in case of conflict; and sometimes even open the door to treaty revision. Sustainable development remains however primarily addressed to States rather than judges, and thus intends to directly constrain the behaviour of legal subjects. Although it may not impose on States an absolute obligation to develop sustainably, it does lay down at least a relative obligation. States must strive to achieve the objective of sustainable development, and in so doing they must adopt a range of measures deemed necessary to its achievement according to the particular set of circumstances. The indeterminate and variable character of the measures necessary for the achievement of sustainable development also narrows down over time and with jurisprudential developments, and the core features of what sustainable development looks like are being slowly identified. As a result, the international judge is today sufficiently well equipped to establish a violation of the obligation to strive to achieve sustainable development.