Salient points so far. Iran has now been hit with three Security Council resolutions under the U.N. Charter’s Chapter VII, which provides for “Action with Respect to Threats to The Peace, Breaches of The Peace, and Acts of Aggression.” In general terms, the Iranian nuclear program now has the status of a “threat to the peace,” and I would argue that its continued nuclear activities are “an act of aggression.”

Article 51 preserves the right of “individual or collective self-defense if an armed attack occurs.” The French-language version of Article 51 uses the phrase “aggression” instead of “attack.” We should always understand Article 51 to have that more expansive meaning.

I argue on NRO today that the capture of the British sailors is intimately linked to Iran’s decision to begin withdrawing from the nuclear nonproliferation regime. The capture was also “an armed attack” for purposes of Article 51 of the Charter. And because Article 51 enshrines “collective self-defense,” the United States, as a British ally, can now invoke Article 51 as cover for any military response to the hostage-taking—and to the related nuclear program.

Therefore, we currently have two bases for invoking Article 51. Such should be the broad outlines of the U.S. legal position now. This legal position would have the virtue of corresponding to strategic reality. The Iranians are seeking to acquire a terrifying offensive capability that will ruin the nonproliferation regime, immeasurably strengthen their freedom of action with respect to conventional aggression, and vastly increase the probability of nuclear terrorism down the road. And it is seeking that capability aggressively, with no regard for the legitimate security concerns of other states. As an Iranian nuclear breakout will result in a grave degradation to national security, we are in the logic of self-defense—the essence of Article 51.