annexation, in international law, formal act by which a state asserts its sovereignty over a territory previously outside its jurisdiction. Many kinds of territory have been subject to annexation, chief among them those inhabited by settlers of the annexing power, those which already have had the status of protectorates of the annexing state, and those conquered by the force of arms. The consent of other interested powers must be obtained in order that the annexation be generally recognized in international law. Efforts to establish the self-determination of inhabitants as the only grounds for the transfer of territory have been realized in the Charter of the United Nations, which does not recognize annexation as an instrument of national policy. The term annexation is also used in municipal government to describe the process by which an incorporated local government may extend its legal control over surrounding areas. Usually this type of annexation requires the consent of the other communities concerned.