International environmental law is composed most prominently of bilateral, regional and global environmental treaties that have been negotiated and ratified by the States that choose to be parties. These treaties address a wide range of issues, including for example the protection of the global atmosphere and oceans (see Chapters 28, 29 and 35), management of transboundary rivers or other shared natural resources (see Chapter 34 and 36), conservation of migratory wildlife or biodiversity (see Chapter 37), and international trade in hazardous substances (see Chapter 32). In addition to this substantial array of international treaties, certain principles of environmental law are emerging as customary or general principles of international law. These principles have formed the basis for a small but growing number of environmental judgments in international tribunals. Together these treaties, principles, and judicial opinions form the body of international environmental law.