Silence has often been studied in international law as a mechanism tied to passivity and oppression. In this study, I propose an exploration of other ontologies of silence by unravelling its possibilities as an active mechanism, namely: (i) a tool for resistance; and (ii) a linguistic device for managing disagreement. For this, I use as an exploratory ground the construction of a non-definition of gender for the crime of persecution in international criminal law (ICL). Analysing the Rome Statute negotiations, I examine how gender-conservative actors successfully opposed the proposal for a non-definition of gender, arguing that such a solution would harm the clarity required by the principle of legality in ICL. By establishing that legal rules must be clear, specific, and cohesive, I argue that the legality principle imposes a burden of speech upon non-state voices in ICL, one that encircles them within a subalternity scheme where speech is demanded but can only be performed or mediated by states. Exploring the negotiations of the Convention on Crimes Against Humanity draft, I examine how the non-definition of gender allowed feminist and queer activists to resist such a burden of speech for the conceptualization of gender. Simultaneously, silence also provided an opportunity for International Law Commission members to propose a draft that avoids cacophony around a contentious term. By reflecting on the active roles of silence, this study contributes to new modes of analysing resistance to dominant modes of legal discourse, as well as exploring dynamics of order(ing) in international law-making.