This article explores the nature of city diplomacy using newly available archives chronicling the ‘municipal foreign policy movement’ of the 1980s, in which US city governments intervened directly in late Cold War foreign affairs issues. Cases covered include US city governments’ involvement in the nuclear free zone movement, the Central American crisis and the anti-Apartheid movement throughout the 1980s. A theoretical synthesis of literature in world society theory, diplomatic studies and social movement theory is used to explain the normative, macro-sociological, legal, demo-cratic and sociopolitical dynamics of contentious city-government intervention in  foreign affairs. Emphasizing the normative processes at play, this article argues through a world society theoretical interpretation that ‘municipal foreign policy’ efforts repre-sent local-level codification of universal norms that the US federal government either neglected to enforce or directly violated.