What is the position of non-state armed groups in public international law, a system conceived for and by states? This article considers the question, mainly in the light of jus ad bellum and jus in bello. It shows that, while armed groups essentially trigger the application of jus ad bellum, they are not themselves endowed with a right to peace. Jus in bello confers rights and obligations on armed groups, but in the context of an unequal relationship with the state. This inequality before the law is strikingly illustrated by the regulation of detention practised by armed groups in non-international armed conflicts. Despite the significant role that they play in modern-day conflicts, armed groups constitute an ‘anomaly’ in a legal system that continues to be state-centric.