Vincent J. Vitkowsky's 2007 ILSA Journal of International and Comparative Law paper addressing the use of force against terrorists under customary international law offers an analytical framework that remains timely and relevant to the international response to the ISIS attacks on Paris:

State practice and patterns of cooperation over the last forty-five years have led to the development of rules of customary international law governing the use of force, in anticipatory self-defense, against terrorists and rogue state collaborators. Although the earlier general rules may have prohibited states from using force except in anticipation of an imminent attack, in more recent practice, the imminence standard has changed. States have initiated and cooperated in the use of force to extend self-defense to instances in which the possibility of an attack is not imminent, but merely expected.

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