SOURCES OF INTERNATIONAL LAW
The sources of international law are provided in “Article 38 of the Statute of the International Court of Justice”. The Statute refers to:
Convention or treaty:-
“An international agreement concluded between states in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its designation”.
International law has developed a vast array of treaties. A treaty may be bilateral i.e., concluded between two states or multilateral i.e., between many states. A multilateral treaty may further be regional like NAFTA or SAARC or it may be Universal like International Covenant on Civil and Political Rights. Some of the most important global treaties are United Nations Charter, Geneva Convention 1949, 1972 World Heritage Convention, 1982, International Covenant on Civil and Political Rights 1966, United Nations Convention on the law of the sea etc.
Custom exists when there is “evidence of a general practice, accepted as law”.
Custom is not time dependent; it is not required for example, that a custom has been in place since “time immemorial” while there is a fair amount of disagreement as to how and whether non-binding resolutions and declarations become customary international law, it may be mentioned that formulation of non-binding principles and their universal acceptance could play an important role in the process of developing customary law. The StockholmDeclaration on the Human Environment and the Rio Declaration on Environment and Development, for example, contains several provisions courts have declared to be part of customary international law.
General Principles of law
The third source listed in the TCJ statute identifies general principles of law as a source from which international law may arise. General principles of law are not the same as customary international law. Custom consists of rules arising out of inter-state practice over time, while general principles of law are those principles that are common to the major legal systems of the world, if not to all of them. They thus are a matter of comparative law, not international law, in origiin. An example could be the right of fair hearing which is recognized as a basic principle of law almost universally and is thus part and parcel of International Law as well.
Judicial Decisions and Doctrine:-
Although the statute of the International Court of Justice refers to judicial decisions as subsidiary sources for determining rules of law, judgments and advisory opinions of the world court and arbitral or other international tribunals are quite important and often are considered as the affirmation or the revelation of customary international rules. The arbitral judgment of March 11, 1941 in the Trail Smelter case is considered as having laid the foundations of international environmental law, at least regarding trans-frontier pollution.
Finally, the writings of eminent jurists provide material sources for identifying the law. International bodies like the International Law Commission of the United Nations as well as national institutes and professional organizations may study and publish authoritative restatements or commentaries on aspects of the law. Individual writer may author treatises and articles examining particular issues in depth that may be of use to judges. For example, Oppenheim treatise is important source for interpreting and understanding International Law