Existing international legal arms control regimes exclude the participation of armed non-state actors, creating a situation where they cannot independently commit to those regimes, experience no sense of legitimate obligation where they do formally apply, face no credible group-level enforcement mechanism, and are not rewarded for compliance. Yet in some cases armed non-state actors do willingly make unilateral arms control commitments. One example is the 54 armed non-state actors who have, in parallel to the Ottawa Treaty regime, renounced anti-personnel landmines through a formal and monitored mechanism created by the international non-governmental organization Geneva Call. Why have some armed non-state actors committed themselves to and complied with this total anti-personnel landmine ban that generally exceeds their preexisting legal obligations? This study explains why and under what conditions armed non-state actors make this commitment. Employing a mixed research methods approach that utilizes statistical analysis of all armed non-state actors engaged by Geneva Call prior to February 2019 on the issue of anti-personnel landmines and four critical case studies, the research demonstrates how armed non-state actors have instrumentalized their commitment to the Geneva Call mechanism as a conciliatory signal to credibly convey their good faith intent toward and interest in a negotiated settlement. The findings expand and enrich previous research on armed non-state actors and highlight how bilateral peace negotiations may contribute to humanitarian commitments that mitigate violent impact on civilians even if a final peace agreement is not readily accomplished. Further, it identifies a window of opportunity for securing this commitment to anti-personnel landmine renunciation and recommends investment in the capacity needed to capitalize on these moments.