International Law and Municipal law are quite different from each other. International Law is the set of rules widely regarded and recognised as binding in relations between nation and states. It only affects nations rather than private citizens and it varies depending on national legal systems. When treaties assign national jurisdiction to supranational tribunals like the European Court of Human Rights or the International Criminal Court, national law may become international law. National Legislation may be forced to adhere to treaties such as the Geneva Conventions.
According to the Black’s law Dictionary, international law means “The legal system governing the relationships between nations; more modernly, the law of international relations, embracing not only nations but also such participants as international organizations and individuals (such as those who invoke their human rights or commit war crimes). It also termed public international law; law of nations; law of nature and nations; jus gentium; jus gentium publicum; jus inter gentes; foreign-relations law; interstate law; law between states.” Public international law regulates that the relationship between international treaties and the provinces. Private international law is a body of law designed to resolve private issues, non-state conflicts affecting more than one jurisdiction or aspects of foregin law.
“Municipal law is the national, domestic or internal law of a sovereign state defined in opposition to international law.” Municipal law means law which deals at national level, state level and local level also. According to the Black’s Law Dictionary, Municipal law defined as “The ordinances and other laws applicable within a city, town, or other local governmental entity.”
Relationship between International Law and Municipal Law
The connection between international law and municipal law is one of the most controversial issues in legal theory such as whether international law and municipal law are part of the whole legal system or two different systems of law. There are many theories in which monistic and dualistic theories are main theories which explain the relationship between international law and municipal law.
As per the Medieval philosophical conception of the world, monism means “a single hierarchically organized legal system. In ancient Judaism, the law was universal, communicated to the people by God.” The law reflected the concepts of reason embedded in nature, the latter being created by God and harmoniously organized with laws with universal validity. The monistic theory states that there was only one set of legal systems that is “domestic legal order.” International law is superior to municipal law as defined under this theory. This theory was developed by the jurist Kelsen. This theory states the connection between international law and municipal law. Kelsen explains that monistic theory states that international law constitutes a single rule of law, as well as separate state legal structures. He also defined that “one can conceive of international law together with the state legal systems as a unified system of norms in exactly the same way as one is accustomed to regarding the state legal system as a unity.” International law is a superior legal order and it is supreme, since it is derived from the practice of states, while the internal or domestic law is derived from the state as defined in international law. As per jurist Lauterpacht, the sovereign state exists on its own. As per the common law approach, international law is deemed to be superior because it provides the strongest protection of human rights for individuals. The rights and duties of some matters will be available in both national and international legal systems that mean the obligations transferred from municipal legal system to international legal system. He believes in the legal order hierarchy that is natural law, international law and finally domestic law. International law is most important as part of the universal legal order.
Dualism is historically embedded in the English positivist school of the 17th century where the concept of monism was reserved, it means the domestic law and international law are two different legal systems. According to Malenovsky, international and municipal laws are focused not only on various jurisdictions and sanction bodies, but also on several subjects and sources. While the relationship between the states is regulated by international law, domestic law governs the rights and responsibility or duties of every individual within states and while international law is derived from custom, domestic law and it is a product of legislation. Dualists claim that while international law is based on the collective will of many nations, domestic law relies solely on one state’s unilateral willingness. International law thus establishes rights and obligations between states which must be decided by each state in the manner in which it compiles. As a result, universal human rights norms that are ratified by dualist states are not enforceable until they have been transformed or implemented into domestic law. As Mc Dougal stated that “the dualistic exhibits as their most distinctive characteristics an attempt to rigidity the fluid processes of world power interactions into two absolutely distinct and separate systems or public orders, the one international law and the other national law. Each system is thus alleged to have its own distinguishable and subjects, distinguishable substantive content. The subjects of international law are said to be states only, while those of national law embrace individuals and the whole host of private associations.”  Dualism states that international law and national law are two distinct legal systems with similar international obligations. There are various legal sources for these two systems. International law is used by two states to solve problems and national law is used within the state for any issues.
Theory of transformation or specific adoption
This theory is based on the dualistic concept. According to this theory, it is the transformation of the treaty into national law that validates the application of the laws laid down in international agreement to individuals alone. Transformation is not a formal requirement but a most important one. International law does not have an obligation by its own force to be applied by municipal court, but if the process of transformation undergoes then the rule of international law will be a part of national law. This theory has mistaken beliefs; firstly, the international law and municipal law are two different legal systems. Secondly, the international law binding only states where the municipal law applies only to individuals is also wrong. According to Strake, “that the rules of international law can be applied when they are transformed into domestic law is not necessary in every case.” Without the transformation, international law cannot be applied to Municipal law. International law is subject to specific adoption by the states. In India, article 51 of Directive principles of our state policy of Indian constitution gives a significant about the obligation and treaties of International law. this article states that “The State shall endeavour to (a) promote international peace and security; (b) maintain just and honourable relations between nations; (c) foster respect for international law and treaty obligations in the dealings of organised people with one another; and (d) encourage settlement of international disputes by arbitration.”
Theory of delegation
According to this theory, when the provisions or terms of theory or convention are to come into force and in what form they are to be integrated into the law of the land or municipal law, there is the delegation of the power or rights to each state to determine it. The transformation of a treaty into national law is not necessary, but the act is entirely an adjunct of one act. The theory of delegation is incomplete because it does not satisfy the main argument of the theory of transformation. It assumes the primacy of international legal order, but the relations between municipal and international law are not clarified. International law is part of the municipal law of those nations, settled by the American decisions. The United States has applied the theory unequivocal that international law is a part of universal law. 
Theory of harmonization
According to this theory, both monistic and dualistic theories did not adequately explain the relationship between the international law and municipal law. The other alternative theories have just explained and developed regarding the harmonisation which is having in international law. As per prof. Niboyet,“ these two forces never meet, they are not like a gear. But like two wheels revolving upon the same axis.” They need not clash and if conflicts arise, municipal law is applied within the internal or domestic legal system, international law is applied to the state and for any breach of obligation of international law.
The relationship between the international law and domestic law is mentioned in the two main theories such as the monistic and dualistic theories. In monistic theory, domestic law and international law are similar laws and there should not be separation among them and it is based on natural law. In dualistic theory, the international law and internal law are not similar and these are the two separate laws. These both theories have their own perspectives about international law but some countries follow one of these theories purely and some countries follow international law when it is in favour of them. The harmonisation theory states that neither theories explain the relation between the international law and internal law.
 Bryan A.Garner(ed.), Black’s Law Dictionary 2392 (8th ed., 2004).
Definition of municipal law, available at: https://www.definitions.net/definition/municipal+law#:~:text=Municipal%20law%20is% (Last visited on December 25, 2020).
 Supra note 1 at 3229.
 Ololade O. Shyllon, Monism/Dualism Or Self Executory: The Application Of Human Rights Treaties By Domestic Courts In Africa, Advanced Course On The International Protection Of Human Rights, Held on (Institute For Human Rights, Abo Akademi University, 17-28 Aug 2009), available at: http://web.abo.fi/instut/imr/secret/kurser/Advanced09/Essays/Working-group4/Shyllon_Monism%20Dualism%20or%20Self%20Executory.pdf (last visited on December 25, 2020).
 David Dyzenhua (ed.), Sovereignty A contribution of the theory of public and international law 17 (Berkeley Law, 2019).
 Supra note 4 at 6.
 Paust, Jordan J., “Basic Forms of International Law and Monist, Dualist, and Realist Perspectives” SSRN 244-265 (2013).
 The Constitution of India, art. 51.
 Relationship between international law and municipal law Flashcards Preview, available at https://www.brainscape.com/flashcards/relationship-between-international-law-an-6088920/packs/9273498 (last visited on December 26, 2020).
 Daniel P O’Connell, “Relationship between International Law and Municipal Law” 48(3) Georgetown Law Journal 440 (1960).
BY BANOTH MYTHILY MEERA NAIK | SYMBIOSIS LAW SCHOOL, HYDERABAD