The starting point of the relationship between international law, and municipal law is represented by state sovereignty, as an absolute dogma. Ultimately, it is the state’s will that establishes the relations with the other states. If the international law coerces the state, it happens because the state has agreed to limit its sovereignty: the state’s self-imposed limitation by its freely complied will to take part in treaties and by the freely acceptance of the customary international law. International law derives its strength from the favourable exercise of sovereign powers by States. The strength international law has recorded in some relevant areas and the weaknesses in others mirrors how much States are willing to direct their sovereign power in support or denunciation of the particular international law provision.
The first port of call in understanding the place of international law in municipal realm is by understanding the sovereignty of states. The term sovereignty has been variously defined. According to W. Michael Reisman, sovereignty has many meanings depending on the context and the objective of those using the word. Accordingly, in Lassa Oppenheim’s words,
There exists perhaps no conception the meaning of which is more controversial than that of sovereignty. It is an indisputable fact that this conception, from the moment when it was introduced into political science until the present day, has never had a meaning which was universally agreed upon.
Sovereignty implies the power and control of the State over both its internal and external affairs. The internal aspect of sovereignty connotes the power of a sovereign to exercise final and absolute authority within it’s territory. The external aspect of sovereignty entails the independence and non-subjection of the sovereign State to any other external authority or control in the conduct of both its domestic and international affairs. It is this aspect of sovereignty that maintains the equality of all states. Thus, the importance of sovereignty stems from its relationship to the equality of states which represents the basic constitutional doctrine of the law of nations.
Furthermore, it is pertinent to note that the basis of sovereignty under international law is Article 2(7) of the United Nations Charter; the essence of which is to give States equal rights to manage their internal affairs free from outside interference and to prevent powerful States from undue intervention in the affairs of weaker States in their relationship with one another. Sovereignty is a cardinal requirement. Sovereignty of states is of ultimate importance to international relations, and also for international legal personality of States. For these reasons and many more, Jean Bodin, described sovereignty as, “the most high, absolute and perpetual power over the citizens and subjects in the commonwealth.”
In the light of the above, sovereignty is the attribute that the State must possess to enable it enter into international legal relations and transform them into domestic regulations and obligations. The very existence of international law and its relationship with municipal law is absolutely the sole product of sovereignty. The current misunderstanding that has crept into the relationship between municipal law and international law, owes largely to the erroneous view that globalization and development of state practice has made away with the traditional absolute right of independent states to exercise supremacy and control in their internal affairs. The ultimate aim of this novel argument is to subjugate the national legal order to international legal order –globalization. In practice, whatever incursion globalization has made into municipal realm is brought about by the strength of municipal law, through the exercise of sovereignty. Owing to this reason, Benedict Kingsbury expressed the situation thus:
Globalization and democratization are placing state sovereignty under strain, as international rules and institutions appear to become more intrusive, transnational civil society more active, and unitary state control less pronounced. State sovereignty as a normative concept is increasingly challenged, especially by a functional view in which the state loses its normative priority and competes with supranational, private, and local actors in the optimal allocation of regulatory authority. But discarding sovereignty in favour of a functional approach will intensify inequality, weakening restraints on coercive intervention, diminishing critical roles of the state as a locus of identity and an autonomous zone of politics, and redividing the world into zones. The traditional normative concept of sovereignty is strained and flawed, but in the absence of better means to manage inequality it remains preferable to any of the alternatives on offer.
In conclusion, by the principles that govern international law, states owe the commitment of respecting the treaties that they ratify and also to determine the application of the treaties by their own legal, executive and judicial institutions. It is pertinent to note that international law doesn’t rule on how the conditions in which legal provisions included in treaties are to be integrated in the states’ domestic legal system, so as they might be applied by the competent authorities. Owing to the recognition of the indubitable sovereignty of a state, this matter of concern is left for the states to decide upon, ruling over it as sovereignties, and concordant with their views on the relation between international law and domestic law. The positivist solutions are inspired by two doctrines encompassed in constitutions or just simply practiced. Accordingly any inquiry concerning the form and shape of international law in the municipal sphere must look up to municipal law of a state for guidance because of the sovereign powers of a state.