Most wars today pit states against armed groups, and talking with such groups is therefore vital for all those working to promote compliance with the law and strengthen the protection of conflict victims. Reaching them, however, involves overcoming material, security-related, legal and political obstacles. What arguments can be invoked to convince armed groups? How can their adherence to international humanitarian law (IHL) be strengthened when they are themselves outlaws according to domestic law? How to engage with armed groups in an international context in which any dialogue may be perceived as a form of betrayal or complicity?