Whether international humanitarian norms are respected during and after civil conflict depends on the behavior of both governments and nonstate 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 states. In a pioneering initiative, the nongovernmental 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 antipersonnel mines, we examine why NSAs would choose to sign conventions that limit their autonomy, and whether such conventions can change the behavior of governments and nonstate armed groups. We propose a game-theoretic model of how the interaction between governments and NSAs shape their incentives to commit to and comply with international humanitarian norms. Our empirical evidence highlights the importance of these interdependencies between governments and NSAs in the realm of humanitarian engagements.