Monism and dualism in international law

The terms monism and dualism are used to describe two different theories of the relationship between international law and domestic law. Many states, perhaps most, are partly monist and partly dualist in their actual application of international law in their national systems. Monists accept that the internal and international legal systems form a unity. Both national legal rules and international rules that a state has accepted, for example by way of a treaty, determine whether actions are legal or illegal. In most so-called "monist" states, a distinction between international law in the form of treaties, and other international law, e.g., customary international law or jus cogens, is made; such states may thus be partly monist and partly dualist. In a pure monist state, international law does not need to be translated into national law. It is simply incorporated and has effect automatically in national or domestic laws. The act of ratifying an international treaty immediately incorporates the law into national law; and customary international law is treated as part of national law as well. International law can be directly applied by a national judge, and can be directly invoked by citizens, just as if it were national law. A judge can declare a national rule invalid if it contradicts international rules because, in some states, international rules have priority. In other states, like in Germany, treaties have the same effect as legislation, and by the principle of Lex posterior derogat priori ("Later law removes the earlier"), only take precedence over national legislation enacted prior to their ratification. In its most pure form, monism dictates that national law that contradicts international law is null and void, even if it post-dates international law, and even if it is constitutional in nature. From a human rights point of view, for example, this has some advantages. For example, a country has accepted a human rights treaty, such as the International Covenant on Civil and Political Rights, but some of its national laws limit the freedom of the press.