What are the sources of international law? The question “what is the international rule?” on any issue can be difficult for an international legal adviser to answer with complete confidence. Unlike domestic law, in international law there are no formal statutes agreed upon by a national parliament nor is there a clear hierarchy of courts to provide legal jurisprudence. Rather, an international lawyer asked for an opinion must glean the law from numerous sources and evidences. As a practical matter, international lawyers will turn to Article 38(1) of the Statute of the International Court of Justice providing that, in deciding a matter in accordance with international law, the Court shall apply: “(a) international conventions, whether general or particular establishing rules expressly recognised by the contesting States; (b) international custom, as evidence of a general practice accepted by law; (c) the general principles of law recognised by civilised nations; (d) subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as a subsidiary means for the determination of rules of law.” In addition to the formal sources and evidences of an international rule, is the concept of pre-emptory norms of international law (jus cogens) from which no derogation by treaty or custom is allowed. Examples include the laws governing piracy, slave trading, torture genocide. Is there any special order of priority for these sources and evidences of law? While there is no necessary order in which each of these sources of international law are to apply, in practice, the order listed in Article 38 will be adopted by courts, tribunals, foreign officers and international lawyers. If the parties to a dispute are also parties to relevant bilateral, regional and multilateral treaties, the provisions of these agreements will have a primary role in describing the legal obligations between them. Where there is no relevant treaty, preference may be accorded to established principles of customary international law or, where necessary, to “general principles of law recognised by civilised nations”. Judicial and arbitral decisions and juristic opinion will also constitute evidence of developing jurisprudence and of State practice for the purpose of determining customary law or the existence of general principles. The primary sources of international law – treaties, custom and general principles- can also provide evidence of the law. A treaty can, for example, be evidence of the practices of States for the purpose of proving a customary norm. A treaty may also, in time, come to reflect a customary norm binding upon States that are not party to the relevant treaty. 29