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U.N. Charter Article 51 recognizes such an inherent right as today, exercised which US and British pilots acted in the NFZ: "if an armed attack occurs" against a U.N. member state, until the Security Council has taken measures necessary to maintain international peace and security.

The right of self-defense could extend even to air strikes outside the zones, if the use of force in the exercise of the right is necessary under the circumstances and proportionate to the use or threat of force being defended against. Under a 19th-century formulation by the U.S. Secretary of State in what is known as the Caroline incident, reaffirmed by the Nuremberg Tribunal after World War II, the necessity must be "instant, overwhelming, and leaving no choice of means, and no moment for deliberation." In the absence of access to classified information, it is not possible to assess how immediate or great a threat the Iraqi air defense facilities posed to the aircraft patrolling the zones today. The immediacy and magnitude of the threat would affect both the necessity and the proportionality of today's air strikes. If both of those tests were met, and if the enforcement of no-fly zones in Iraq is permissible under U.N. Security Council resolutions, the self-defense argument is strong.