Whether international humanitarian norms are respected during and after civil conflict depends on the behavior of both states and non-state actors (NSAs). However, international conventions on the protection of civilians generally do not address NSAs, as such conventions are open only to the representatives of state parties. In a pioneering initiative, the non-governmental organization Geneva Call has started to address this problem, by soliciting NSAs to sign `deeds of commitment' to ban particular activities violating humanitarian norms. Focusing on the case of anti-personnel mines, we examine why non-state actors would choose to sign conventions that limit their autonomy, and whether such conventions can change subsequent behavior. We propose a game-theoretic model of how the interaction between NSAs and states shape their incentives to commit to and comply with international humanitarian norms. Our empirical evidence highlights the importance of these interdepencies between governments and NSA in the realm of humanitarian engagements.