The article addresses the topic of the constitutionalization of international law starting from the reasons why international law began to be introduced into constitutional texts. This was the result of, among other things, the growth of international organizations, the tightening of relations between the various subjects of international law, the promotion of human rights, the desire to prevent the drama of war and, finally, the processes of integration and globalization. The process of incorporating international law into the constitution was also not indifferent to the French Constitution, which provides a number of provisions expressing the principle of favourability (openness) to international law. The article analyzes in detail the position of French doctrine, addressing the subject of the purposive assumptions of the constitutionalist procedure, as well as praxeological assumptions.