Recent months have provided ample evidence of the tragic harm that armed groups can cause to civilians when they use armed force against their enemies. The concerns of the editors of this anthology are the ‘conditions of life experienced by the 60 million civilians living under’ the control of armed groups, and whether international law can ‘offer perspectives to alleviate them’. They invite the readers to see armed groups as ‘more than parties to armed conflict, terrorist or military entities’. Contributors discuss various aspects of de facto governance exercised by armed groups, such as education, health care and criminal justice. For example, Helen Duffy discusses whether armed groups can hold criminal trials, how they may do so and for which crimes. Marta Furlan discusses the healthcare practice of armed groups in Syria and Afghanistan and how their governance systems relate to international humanitarian law, international human rights law and Sharí’ah. Operating at both domestic and international levels, armed groups may be unlawful under domestic law (violating the State’s monopoly to use of force, they are often designated as ‘terrorist organisations’, barring co-operation), while subject to international law obligations in armed conflicts. Armed groups sometimes also create ‘legal’ systems parallel to that of the state they operate in. It is this co-existence of normative frameworks which the book refers to as a ‘shadowland of legality and illegality’. Benefitting from contributions by outstanding experts on armed groups, this book could hardly be more topical than it is now, but it presupposes basic knowledge of international humanitarian law and how it applies to non-international armed conflicts.