This paper assesses the rise and decline of international rule of law in the case of non-state armed actors. Both signs of rise and signs of decline of international rule of law show in the case of non- state armed actors. Signs of rise include the expansion of coverage of international humanitarian law (IHL) and international criminal law, as well as international legal argumentation and rhetoric made by non-state armed groups. Some non-state armed actors express that they are governed by IHL in public statements or bilateral agreements with international actors, partly acknowledging universality of international humanitarian norms, and sometimes act as such. Signs of decline in the international rule of law also show – although some of them can be seen as business-as-usual – privileging of military advantage, instrumental use of international law (as justification and local interpretations), as well as conflicting understanding of IHL between local and global norms. The multiplicity of non-state actors also portends the decline of international rule of law, with the proliferation of many non-organized groups without legitimacy-seeking motivations.