ABSTRACT
The principle applied in Trail Smelter has been more generally recognised. Article 3(1) of the International Law Association (ILA) 1982 Montreal Draft Rules on Transboundary Pollution restates customary international law as requiring States to prevent transfrontier air pollution so that no substantial injury is caused in the territory of another State (International Law Association, 60th Report, 1982). On the basis of this provision, Sands suggests that, ‘(G)eneral principles of international environmental law, as reflected in State practice, treaties and other international instruments, provide strong support for the view that customary international law prohibits States from causing significant environmental damage from transboundary atmospheric pollution’ (Sands (1995) 247). However, Birnie and Boyle point out that ‘a rule of this generality, applicable only in inter-State claims, has proved to be of limited utility’. They go on to argue that a rule intended mainly to compensate for serious harm is unsuitable for determining the content of obligations of diligent control and prevention of air pollution. For this purpose ‘more detailed standards are required to implement a fully preventive approach. These can only be created through negotiation and international co-operation’ (Birnie and Boyle (1992) 394).
