Relationship between International law and Municipal Law
International Law is the law that governs the Relations of sovereign independent States inter se Municipal law or State law or national law is the law of a State or a country and in that respect is opposed to International Law which consists of rules which civilized States consider as binding upon them in their mutual relations.
Kelsen observes that national law regulates the behavior of individuals International law is the behavior of States or as it is put whereas national law is concerned with the international relations the so-called domestic affairs of the State. International Law is concerned with the external relations of the State its foreign affairs.
The legislature and court systems are different on the international and municipal levels. Where the municipal level uses a legislature to help enforce and test the laws, the international court system relies on a series of treaties without a legislature which, in essence, makes all countries equal.
Enforcement is a major difference between municipal and international law. The municipal courts have a law enforcement arm that helps require those it determines to follow the rules, and if they do not they are required to attend court. The international court system has no enforcement and must rely on the cooperation of other countries for enforcement.
There is a divergence of opinion on the question as to whether International Law and Municipal Law on the various national laws can be said to form a unity being manifestations of a single conception of law or whether International Law constitutes an independent system of law essentially different from the Municipal Law.
The former theory is called monistic and the latter dualistic.
Monists assume 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 monist states, a distinction between international law in the form of treaties, and other international law, e.g. jus cogens is made. International law does not need to be translated into national law. The act of ratifying the international law immediately incorporates the law into national law. 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, the latter has priority. In other states, like in Germany, treaties have the same effect as legislation, and by the principle of lex posterior, 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 predates international law, and even if it is the constitution. It maintains that the subject of the two systems of law namely, International Law and Municipal Law are essentially one in as much as the former regulates the conduct of States, while the latter of individuals. According to this view, the law is essentially a command binding upon the subjects of the law independent of their will which is one case is the States and in the other individuals. According to it International Law and Municipal Law are two phases of one and the same thing. The former although directly addressed to the States as corporate bodies are as well applicable to individuals for States only group.
Dualists emphasize the difference between national and international law and require the translation of the latter into the former. Without this translation, international law does not exist as law. International law has to be national law as well, or it is no law at all. If a state accepts a treaty but does not adapt its national law in order to conform to the treaty or does not create a national law explicitly incorporating the treaty, then it violates international law. But one cannot claim that the treaty has become part of national law. Citizens cannot rely on it and judges cannot apply it. National laws that contradict it remain in force. According to dualists, national judges never apply international law, only international law that has been translated into national law. According to the dualist view, the systems of International Law and Municipal Law are separate and self-contained to the extent to which rules of the one are not expressly or tacitly received into the other system. In the first place, they differ as regards their sources. The sources of Municipal Law are customs grown up within the boundaries of the State concerned and statutes enacted therein while the sources of International Law are customs grown up within the Family of Nations and law-making treaties concluded by its members. In the second place, Municipal Laws regulate relations between the individuals under the sway of a State or between the individuals and the State while International Law regulates relations between the member States of the Family of Nations. Lastly, there is a difference with regard to the substance of the law in as much as Municipal Law is a law of the sovereign over individuals while International Law is a law between sovereign State which is arrived at an agreement among them.