A U.S. president has just received word that American counterterrorist operatives have captured a senior al Qaeda operative in Pakistan. Among his possessions are a couple of cell phones–phones that contain several American phone numbers. In the wake of Sept. 11, 2001, what’s a president to do?

If the president were taking the advice offered by some politicians and pundits in recent days, he would order the attorney general to go to the Foreign Intelligence Surveillance Court. The attorney general would ask that panel of federal judges for a warrant under the Foreign Intelligence Surveillance Act (FISA) to begin eavesdropping on those telephone numbers, to determine whether any individual associated with those numbers was involved in terrorist activities.