This research examines an attribution to state sovereignty - the power of states to confer competences on international organisations. Firstly is examined what powers states so confer – legislative, executive or judicial, exclusive or shared, express or implied, revocable, semi- revocable or non-revocable, specific or general, mere functional, specified, immediate or contingent, prior or ex post facto, clear or vague or subsidiary. Thereafter is examined how are the powers conferred. Here are mostly examined the conferrals by international treaties – „common“ international treaties, constituent international treaties that can form the basis for further delegation, and for supranational law-making. Finally is examined conferral of powers by the Estonian State on international organisations. The rights, obligations and responsibility for international commitments in the pluralist world depend on the forms and methods used for conferral of powers. The book is primarily aimed at law students and lawyers, but could be read by anyone who is interested in the position of a state as an international actor towards international organizations.