Summary

Annexation refers to both the unlawful and the lawful incorporation of a territory and its people into another state. In contemporary international law, unilateral annexation of a territory is unlawful. It was not always so. Previous international law recognized a right of conquest and other modes of acquiring territory without popular consent. Unification of territories accomplished through authentic processes of consent may, however, lead to annexation that is lawful, both domestically and internationally. The subdisciplines of international law, international relations, and comparative politics respectively have distinct literatures on annexation. International law addresses its normative appropriateness, international relations examines whether the incidence of unilateral annexation has declined because of legal prohibitions or for other reasons, and scholars of comparative politics address why governments may annex territories—among other options.