During non-international armed conflict, war crimes often go unpunished in areas where state authorities are unable to enforce the law. While states are under a customary law obligation to investigate and prosecute war crimes committed on their territory or by their nationals, the Customary International Humanitarian Law Study of the International Committee of the Red Cross has not found that this obligation extends to armed non-state actors (ANSAs). Nevertheless, command responsibility requires the individual commander to punish their forces in case war crimes have been committed and a growing amount of state practice demanding similar commitments — both legally and politically — from these actors as such can be observed over the past two decades. Indeed, ANSAs routinely impose penal sanctions onto their subordinates and often establish judicial structures in order to do so. This article argues that whereas ANSAs should be under some form of obligation to ensure accountability, alternative solutions to makeshift courts and penal proceedings might be better suited to prevent impunity and maintain fair trial guarantees.