Not very long ago the regulation of warfare by international law was conveniently organized according to several sets of dichotomies: the right to use force was determined by the presence or absence of an actual armed attack; the type of the military conflict was either international or internal, each with its unique set of norms; the regulation of the hostilities was founded on the dichotomy between combatants (and military targets) and noncombatants (and nonmilitary targets); and the obligations of parties to the conflict and those of neutral third parties were strictly distinguished. But, perhaps due to its counterintuitiveness, the most prominent of all dichotomies has been the sharp distinction between the jus ad bellum, the law governing resort to force, and the jus in bello, the law governing the conduct of hostilities.
Rethinking the Divide Between Jus ad Bellum and Jus in Bello in Warfare Against Nonstate Actors,
Yale J. Int'l L.
Available at: https://digitalcommons.law.yale.edu/yjil/vol34/iss2/12