The 11 September 2001 (9/11) attacks on the World Trade Center and the Pentagon transformed America's view of the world. In response to these unprecedented terrorist attacks, the Bush Administration devised the Bush Doctrine; a new military strategy intended to reduce the risk of future terrorist threats. Where the US Cold War military strategy had focused almost solely on threats posed by the Soviet Union and relied on deterrence, the post-9/11 strategy focuses on threats from smaller (state and non-state) actors and relies on preemptive strikes against terrorists and states suspected of developing nuclear, biological, and chemical weapons. The easily identifiable and containable Cold War threats stand in stark contrast to the amorphous, and often ambiguous, dangers posed by al Qaeda and other terrorist groups. Post-9/11 threats have made Cold War strategies of deterrence and containment irrelevant.

Does the Bush Doctrine of preemption comport with the law of self-defense?

Under a restrictive view of Article 51, for example, an armed attack against the United States should have occurred for the United States to justify an attack in self-defense. To assess the lawfulness of any preemptive action, two questions must be answered. First, is there a right to act (jus ad bellum)? Second, if the answer to the first question is yes, is the preemptive action necessary and proportional? That is, can weapons be deployed and used that discriminate between combatants and civilians? Like any other unilateral action, the rationale to justify this action would include the absence of a plausible international institutional alternative. Under a strict reading of the law pertaining to self-defense, the Bush Doctrine satisfies neither criterion for legality.

The text of Article 51 explicitly requires an "armed attack" as a pre-condition for the retaliatory use of defensive force. The intent of the Charter's framers was to make the acceptable uses of force clearly distinguishable from unacceptable uses of force. Drawing the line at the precise point of an armed attack, an event the occurrence of which could be objectively established, served the purpose of eliminating uncertainty. In the case of Iraq, the fact of an armed attack by Iraq on America or American targets was not present. Further, the international response to Israel's bombing of Iraq's Osirak reactors in 1981 indicates that a mere probability of future nuclear attacks by a hostile state will not provide a legitimate claim of self-defense.

The U.S. justification for the preemptive attack was the alleged manufacture by Iraq of nuclear, chemical, and biological weapons. A state may legitimately engage in preemptive strikes when the threat is immediate. In the case of Iraq, the imminence of the threat was unclear. However, the United States exercised this option by addressing the Security Council on multiple occasions and lobbying Security Council members individually. The inability of the United States to persuade other Security Council members that Iraq posed such a threat to international peace cannot substantiate the imminency requirement.

Nor was the proportionality requirement satisfied as articulated in the Nicaragua v. United States. The principle of proportionality necessarily prohibits action broader than the action undertaken in the Nicaragua case in response to a provocation that is less substantial than the provocation posed. Specifically, the US action against Nicaragua (attacks on its ports and oil installations) constituted a disproportionate response to Nicaragua's action against El Salvador (the provision of arms and assistance to anti-government rebels). It, therefore, follows that an even graver action against Iraq (invasion and the overthrow of the government) necessarily constituted a wholly disproportionate response to a lesser indeed, non-existent provocation.

A liberal interpretation of Article 51 allows states to take actions to anticipate an imminent attack like conducting a preemptory strike. But there was no evidence of an imminent attack from Iraq. The timing element mandates that the response is proximate in time to an imminent threat of attack. Here, the period between the United States' determination that an attack was imminent and its action to stop it took a long time. In the case of Afghanistan, there was no need to extend the existing legal framework since an 'armed attack' had occurred on  the US which had been plotted on Afghan territory. But, in the Iraq case, the use of force in a self-defense/ preemptive mode was wrong since the tests of proportionality and duration were clearly lacking. The lack of any Security Council approval or involvement is another fundamental flaw with these actions in the 'War on Terror'.