Self-Defense and the Use of Force: Breaking the Rules, Making the Rules, or Both?

This article examines shifts in international law regarding the use of force—the jus ad bellum —that emerged in the wake of the September 11, 2001, terrorist attacks and subsequently were invoked in part by the United States and United Kingdom to justify military intervention in Iraq. These shifts import some elasticity—in time, space, and place—into the preexisting legal understanding of self-defense. To be sure, the general consensus that supported the use of force in Afghanistan as a legitimate exercise of self-defense has diluted as the use of that force expanded into other theaters of operation. It is therefore unsurprising that considerable controversy envelops claims by some states that international law entitles them to use force in self-defense in a preemptory manner. This article explores the articulation of this and other justifications for the military intervention in Iraq. It also unpacks the difficult question whether these entitlements are constitutive of inchoate legal rules or simply deviations from the still operational old rules. Moreover, this article encourages scholars and students of international law and relations to consider why a movement is afoot to change the rules and how this affects the architecture of collective security. To facilitate this process of reflection, this article explores the policy implications of retaining the old rules or adopting the newly alleged rules.