The monography provides an analysis of the importance and complexity of state sovereignty’s nature changing and its implementation in the process of transferring authority to supranational institutions. It deals with the complex description of the Ukraine’s participation in supranational organizations, the problems of transfer mechanisms, evolution of the national legislation. In this context the authors justify the development of practical procedures to legitimize the process of authority transfer in order to guarantee the all participants’ balance of interests and strengthen their political stability. This work integrates the unique classification and research materials. By the reflection of this type the authors lay the base for continuing further researches of the integrational tendencies of post-Soviet states and the degree of their sovereign powers’ transfer to supranational institutions.