On 23 September 1920, when the Inter-Allied boundary commission arrived in the town of Gmünd (Cmunt), residents participated in a large demonstration about the small border change set to take place along the Lower Austrian-Bohemian border. While boundary commissions in Europe have historically acted as intermediaries between local and state interests, this article argues that the Inter-Allied commission members departed from this role when they refused to undergo any public consultation or meet with any demonstrators about the border change. Examining the (in)actions of the postwar Inter-Allied and state boundary commission representatives alongside the concerns of the local population in Gmünd reflects how international, state, and local actors all perceived Europe’s boundaries as malleable and negotiable over a year after the signing of the post-World War I (WWI) treaties. The lead-up to and demonstration in Gmünd in September 1920 further nuances the relationships between the Allied Powers, postwar states, and local populations during the boundary-making process in the wake of WWI, illuminating both successful and unsuccessful claim making strategies pursued by state and local actors.