Forced marriage,as a systematic form of gender-based violence,is pursued in contemporary international criminal law discourse not only as a gross violation of human rights but also as a crime against humanity.Although the Rome Statute does not explicitly criminalize forced marriage, the jurisprudence of international tribunals has deemed it prosecutable under the general heading of ‘‘other inhumane acts’’.The central question of this article is not how this act criminalized,but its legitimacy in relation to the fundamental principle of nullum crimen sine lege.This principle,a cornerstone of defendants' rights, finds itself in an unavoidable tension with the judicial development of international crime categories to address new forms of systematic violence.Adopting a critical-analytical approach, this article argues that prosecuting forced marriage under ‘‘other inhumane acts’’,despite its seemingly contentious nature,does not violate the principle of legality.Rather,it represents a necessary and legitimate manifestation of ‘dynamic interpretation’ in international criminal law,enabling it to respond to the evolving nature of systematic violence.While this path has been solidified through established jurisprudence, particularly the Dominic Ongwen case,the article concludes that to resolve lingering ambiguities and further safeguard defence rights,the explicit inclusion of this crime in the Rome Statute and the draft Crimes Against Humanity Convention is an imperative next step.