This article proposes an alternative to the conventional way of deciding when a State may target or detain members of an armed group. Instead of asking whether there is an armed conflict between the State and the group, this article argues that we should look at the State’s justification for the use of force against the group or its members. In a non-international context, this justification is rooted in human rights law. For this reason, the authorization for the resort to force operates on an individual basis, and the State is only justified in using force against individual members of non-state groups when it is necessary and proportionate to the defense of life or the restoration of public order. Crossing the threshold of armed conflict does not alter the basis on which the justification for the use of force is assessed. Therefore, the justification for the use of lethal force in non-international armed conflict (NIAC) depends on the threat posed by individual fighters and the context where they are encountered. The justification for security detention is based on threat rather than membership of an armed group, and takes account of the length of time for which individuals have been held. The article argues against the use of international humanitarian law to determine the substantive content of human rights law in NIAC, but suggests that human rights law must be interpreted in a context-specific way. The article then sketches some possible consequences of this framework for military campaigns against domestic and extraterritorial armed groups, and considers some possible objections.