As international humanitarian law (IHL) is binding on non-state armed groups (NSAGs) without their having participated in its development and adoption, for effective compliance it is key that NSAGs give their actual consent to be bound by IHL norms. Various legal instruments are, and can be, used to this effect: unilateral declarations, codes of conduct, special (bilateral) agreements and multilateral agreements. All these instruments have their advantages and drawbacks. The most important drawback is probably that NSAGs use these instruments to curry favour with the international community, without their having internalized the norms or having provided for a rigorous system of monitoring compliance with the norms laid down in the instruments. However, some outside actors have made commendable efforts to engage NSAGs with a view to improving compliance, such as the ICRC, Geneva Call (an NGO) and the UN Security Council. Given the nature of NSAGs—they are often ragtag bands whose goals determine their means—it is not always self-evident to draw their attention to compliance with IHL norms. International actors have to tread carefully, but sanctions should not be eschewed in case of persistent breaches of IHL. Such sanctions may include travel bans, and prosecution of both NSAGs and their leaders under international criminal law.