Due to their specific legal nature, the jus cogens rules occupy a special place and have conceptual significance in international law system in the vein that their non-compliance may, in fact, sabotage foundations of the international legal system based on states consent. Since the entry into force of the VCLT, jus cogens concept in international law has moved closer to international legal practice. A paradoxical situation exists - jus cogens concept in international law is generally accepted, there is also a normatively established definition of such a rule, but its specific framework and content remain unclear. The ICJ has repeatedly addressed the issue of jus cogens norms, but a detailed concept on jus cogens has not been formed. It is analyzed that the problem of establishing jus cogens is difficult to solve in abstractio. The reason lies not only in the absence of a single official list of norms jus cogens – the criteria for including norms in such a list are not defined. Opinions of representatives of the doctrine and the international judiciary on this issue differ significantly. Addressing the problem of the role and significance of jus cogens, general international law imperative rules, for the observance and interpretation of treaties, it should be noted that treaties are to be interpreted in a format compatible with the imperative norms. The considerations presented in the research indicate a special, if not decisive, role in the observance of jus cogens in treaties interpretation.