This article analyses the legal classification framework applicable in cross-border non-international armed conflicts (NIACs) through the lens of international humanitarian law (IHL). It defines cross-border NIACs as armed conflicts involving a state or a multinational force, engaging non-state armed groups on the territory of another state, with or without that state’s consent; as well as hostilities between non-state armed groups across state borders. Where a state acts without the territorial state’s consent, overlapping legal classifications may arise, necessitating use of the ‘double classification’ method. Common Article 3 of the Geneva Conventions and customary IHL are identified as the core legal sources that apply to this variation of NIAC, while the potential extraterritorial application of Additional Protocol II 1977 (AP II) is considered in the light of the analogy with international human rights law. The article contends that when a state exercises effective control over persons in cross-border NIACs, obligations under AP II may extend extraterritorially to its armed forces.
