David Ignatius:

Last October, the Yemeni government came to the CIA with a request: Could the agency collect intelligence that might help target the network of a U.S.-born al-Qaeda recruiter named Anwar al-Aulaqi?

What happened next is haunting, in light of subsequent events: The CIA concluded that it could not assist the Yemenis in locating Aulaqi for a possible capture operation. The primary reason was that the agency lacked specific evidence that he threatened the lives of Americans — which is the threshold for any capture-or-kill operation against a U.S. citizen. The Yemenis also wanted U.S. Special Forces’ help on the ground in pursuing Aulaqi; that, too, was refused.

Even if the CIA had obtained hard evidence in October that Aulaqi was a threat, and Special Forces had been authorized for a capture operation, permission from the National Security Council would have been needed. That’s because any use of lethal force against a “U.S. person,” such as Aulaqi, requires White House review.

The subsequent chain of events was a chilling demonstration of Aulaqi’s power as an al-Qaeda facilitator: On Nov. 5, U.S. Army Maj. Nidal Hasan killed 13 of his fellow soldiers at Fort Hood, Tex.; Hasan had exchanged 18 or more e-mails with Aulaqi in the months before the shootings, according to the Associated Press. Then, on Christmas Day, Umar Farouk Abdulmutallab, a Nigerian who had been living in Yemen, tried to blow up an airliner bound for Detroit; he is said to have confessed later that Aulaqi was one of his trainers for this mission.