List of national legal systems
Common law is currently in practice in Ireland, most of the United Kingdom (England and Wales and Northern Ireland), Australia, New Zealand, Bangladesh, India (excluding Goa), Pakistan, South Africa, Canada (excluding Quebec), Hong Kong, the United States (on a state level excluding Louisiana), and many other places. In addition to these countries, several others have adapted the common law system into a mixed system. For example, Nigeria operates largely on a common law system, but incorporates religious law.
International law
International treaty law comprises obligations states expressly and voluntarily accept between themselves in treaties. Customary international law is derived from the consistent practice of States accompanied by "opinio juris", i.e. the conviction of States that the consistent practice is required by a legal obligation. Judgments of international tribunals as well as scholarly works have traditionally been looked to as persuasive sources for custom in addition to direct evidence of state behavior. Attempts to codify customary international law picked up momentum after the Second World War with the formation of the International Law Commission (ILC), under the aegis of the United Nations. Codified customary law is made the binding interpretation of the underlying custom by agreement through treaty. For states not party to such treaties, the work of the ILC may still be accepted as custom applying to those states. General principles of law are those commonly recognized by the major legal systems of the world. Certain norms of international law achieve the binding force of peremptory norms ("jus cogens") as to include all states with no permissible derogations.International law is sourced from decision makers and researchers looking to verify the substantive legal rule governing a legal dispute or academic discourse. The sources of international law applied by the community of nations to find the content of international law are listed under Article 38.1 of the Statute of the International Court of Justice: Treaties, customs, and general principles are stated as the three primary sources; and judicial decisions and scholarly writings are expressly designated as the subsidiary sources of international law. Many scholars agree that the fact that the sources are arranged sequentially in the Article 38 of the ICJ Statute suggests an implicit hierarchy of sources. However, there is no concrete evidence, in the decisions of the international courts and tribunals, to support such strict hierarchy, at least when it is about choosing international customs and treaties. In addition, unlike the Article 21 of the Rome Statute of the International Criminal Court, which clearly defines hierarchy of applicable law (or sources of international law), the language of the Article 38 do not explicitly support hierarchy of sources.