The relationship between international law and national law as well as the concept of supremacy of international law are currently very controversial issues. Many authors accept the supremacy of international law as a value that allows the existence of an international legal rule.Although the domestic law of many states in today’s conditionscomply with the ever-increasing demands of international law, it is generally refused to accept the unconditional supremacy of international law on constitutional principles. Most states have declared their supreme constitutions.Some international treaties obligate States Parties to adapt their national legislation or to undertake other measures to meet with the international obligations they have undertaken. States have the right not to become part of an international act that may be in conflict with their constitution. They can also avoid the conflict between the international act and their constitution by making a reservation against the international act in order to protect their domestic law projections and to prevent conflict at international level or by amending their constitution.There is a principle according to which it is the internal law that permits the application of international law in the domestic legal system, since international acts must first be ratified by the parliaments of states in order to become part of the interior right of a state.