Customary International Law and the Environment

Despite the large number of environmental agreements at the global, regional and bilateral levels, the role of customary international law remains of great importance in practice. First, many treaties which are in force remain largely unimplemented. Secondly, treaties only bind those States that have become parties to them, and that introduces sometimes important variations in the scope of environmental agreements. Thirdly, there is at present no treaty formulating binding overarching principles interweaving sectorial environmental agreements. As a result, it is often necessary to go back to the level of customary norms when certain difficulties of interpretation or implementation arise. Fourthly, custom is important to conciliate a range of environmental and non-environmental interests (e.g. trade, human rights, investment, armed action) governed by different treaties. Last but not least, custom plays an important role in disputes concerning a disputed area or where there is no applicable treaty. In this context, this chapter examines two main questions. Section II analyses the process of custom formation with reference to environmental protection in order to show both the ‘banality’ of this process but also its peculiarities. Section III focusses on the content of customary international environmental law as recognised in the case-law, both old and new