The field of international environmental law is one of the most dynamic and growing fields of international law. By some estimates, more than eight hundred multilateral and bilateral agreements now contain provisions dealing with one o:r more aspects of the environment. In addition, several key decisions by international tribunals and arbitral panels have recognized the existence of customary international environmental law. “Soft law” principles and concepts, though by their nature non-binding, also occupy a prominent position in the emergence of international environmental !aw. Thus, for example, the Precautionary Principle and the Polluter Pays Principle help to fill gaps left by the treaties and cases. Over time some- of these principles and concepts may become binding customary law, although most of them have probably yet to achieve this status. Finally, a growing number of international institutions, including the U.N. Environment Programme, the U.N. Commission on Sustainable Development, the World Health Organization, the U.N. Food and Agriculture Organization, the U.N. Development Programme and the multilateral development banks issue environmental standards and guidelines.
At least three trends in international environmental law suggest that the future may see an increasing internationalization of U.S. national and subnational environmental law: (1) a growing focus in international environmental law on implementation and compliance; (2) a change in the classification of which environmental issues are international; and (3) the development of international principles aimed directly at strengthening national environmental law.