Our experts agree that, having sustained an unlawful armed attack, the U.S. has the legitimate right to self-defense under Article 51 of the UN Charter. The U.S. would have no obligation to obtain prior authorization from the UN Security Council, but must report to the Council any actions so taken. David Turns notes that, “the need for response [must] be instant and overwhelming, with an element of urgency… The longer the U.S. waits before responding militarily to the September 11 attacks, the less it may look like pure self-defense.”

For the first time ever, the NATO Charter—which declares an attack on one member State to be an attack on all members—was invoked, and this could yield an unprecedented cooperative effort. No prior authorization is needed from NATO for a unilateral U.S. response.

At the same time, all our experts stressed the importance of building and maintaining a multi-national coalition to end the deadly menace of terror. “If threats work, so much the better,” says Eyal Benevenisti, “if they encourage cooperation from factions who have harbored bin Laden (assuming he is responsible).”