The use of force against non-state actors by states has both "internal" and "international" dimensions, according to Henderson. The threshold between the two is fluent and the determination of permissible "internal use of force" (co-)determines the (inter)national status of armed non-state actors. That qualification determines whether the use of force against non-state actors is permitted under the rules of the UN Charter, and whether, consequently, a state is legally responsible for its resort to the use of force. The use of force against terrorists has raised particular questions in international legal literature. Henderson seems to conclude that non-state actors have changed the character of the use of force and so have they affected a change in the application of the rules, in particular proportionality and necessity.