This lecture held by Lachezar Yanev and Harmen van der Wilt examines how the concept of universal jurisdiction has evolved through both historical practice and contemporary state engagement. First, newly declassified records from the UN War Crimes Commission are discussed to reveal that universal jurisdiction was broadly accepted in the body’s work immediately after the Second World War. Following that, empirical findings from fifteen years of state submissions to the UN General Assembly’s Sixth Committee will be presented, illustrating how states articulate and shape their acceptance of universal jurisdiction over core international crimes today. Finally, current state practice will be discussed, showing how domestic prosecutions are (re)defining the field of international criminal law and pushing the boundaries of ‘war crimes’ through innovative judicial reasoning and legislative developments.