The article analyzes Allied attempts to try German war criminals after the First World War and the ensuing Leipzig trials. Historians of international law commonly describe these as the first (failed) attempt to break principles of national sovereignty by implementing principles of international humanitarian law, which were later realized at Nuremberg and The Hague. The article brackets the question of the Leipzig trials’ alleged success or failure by situating them not so much within the long-term history of international justice but, rather, within the political and intellectual culture of Weimar Germany. The article shows how the German government tried to use its limited domestic sovereignty in order to enhance its international sovereignty. By asking how German sovereignty was contested, negotiated, and reaffirmed, the article historicizes the Leipzig trials and also addresses the more general question of which conditions facilitate international war crimes trials. Drawing on the literature on transitional justice, this article suggests that contestations over German domestic and international sovereignty after the Versailles Treaty offer a more productive frame to understand the trials than measuring success according to international humanitarian law.