Customary international law also provides some general guidance on the legal implications of climate change . An unwritten international norm becomes part of customary law if it is consistently followed over a long period of time by a significant number of states which accept it as a legal obligation. For example, if a particular commitment to act is repeatedly expressed at important international conferences, and if all the participating states act in accordance with it, then the commitment may become an obligation under customary law. Existing customary law affirms the sovereign right of states to manage their own natural resources, although this right is by no means absolute. Customary law also prohibits a state from allowing activities on its territory to inflict serious damage on the environment of other states or on parts of the environment that do not belong to any state.
Customary law has no definitive answer.
Until 1992, international law did not address climate change directly. Because climate change is a phenomenon of unprecedented scale and character, traditional legal concepts and mechanisms provided by treaties and customary law do not help much. A number of treaties already in force, notably the Geneva Convention on Long-Range Transboundary Air Pollution and the Montreal Protocol on Substances That Deplete The Ozone Layer , do deal with atmospheric pollution. However, they do not specifically address the causes and effects of climate change as such. The treaty drafters referred to the statements to evaluate the concerns and proposals of various states and regions.