To know the relationship between International law and Municipal law, it is important to know what these to laws are. International law is the rules and conducts which deals with the conduct of states. To put into simpler terms, the international law is a set of rules in which the countries use in dealing with each other. The Municipal law is the internal law of the land. There are different theories that distinguish the difference of the two laws.
The dualists or the pluralist theory states that international law and municipal law are different with each other in terms of their source, the relations they regulate, and their substance. Both of the laws differ in source because the international law came from treaties and customs grown among states while the municipal law is a product of local or domestic custom.
They differ in the relations they regulate. How? The international law regulates the relationship of states with one another and is concerned with the external and foreign affairs of the state while the municipal law regulates the relationship of individuals under the state and is concerned with the domestic affairs of the state. They also differ in their substance. The international law is a law between sovereign states while municipal law is the law of the sovereign over the individuals in the state. In this theory when a conflict arises as to whether what law should be used in dealing with an issue, the municipal law prevails.
The dualists are positivists that biases greatly on state sovereignty. Next theory is the monistic theory or monism. In this theory, the international law and the municipal or domestic law are under one system of law. But there are two monistic theories that states what law should be used in settling disputes or the likes. One monistic theory has a stand that international law is superior to municipal law which is supported by Kelsen.
It holds that international law is superior to municipal law because monistic theorists believe that international law can instill domestic order. Kelsen also believes that the international law encompasses every aspect of human life. Monistic theorists also see international law as a collective outcome of different local sovereigns. The other monistic theory believes that municipal law is superior to the international law