The trouble was that neither the administration nor the Democratic leaders in Congress and their ranking members on the Senate and House intelligence committees (all of whom had been briefed by the administration on what it was doing) felt comfortable explaining publicly why everything allegedly had to be done so rapidly. Evidently, the explanation would reveal to the public (and hence to the terrorists) various secret techniques used by the government in the course of surveillance. So it was effectively impossible to explain why the administration had refused to seek court permission first.
Now, however, there is a ray of light on this crucial question. In a review of Risen's book in the Feb. 5 issue of The New York Times Book Review, Walter Isaacson, president of the Aspen Institute, states that the criticized program "involves electronically scanning hundreds of calls and e-mail messages."
He doesn't specify a time frame, but it is reasonable to assume that we are talking here about hundreds of messages per day, or even per hour. No doubt the vast majority of such messages turn out to be innocent, but this cannot be known until they are scanned. And what the Democrats are contending is that the administration ought to have sought prior permission from a FISA court to scan each individual message (or at least to have done so, as the law allows in emergencies, within 72 hours after the scan).
This is obviously impossible. Even if our intelligence officials could somehow isolate every communication between someone here and someone abroad, and bring each individually to the attention of a FISA court to seek approval for monitoring it, doing so would inevitably take many hours, by which time the communication would long since be over. And even with a 72-hour grace period in which to obtain retroactive approval, the burden of ruling on each of the thousands of applications would quickly overwhelm the court.
This overview of the practicalities, moreover, almost certainly understates the problem. Undoubtedly, there are further technological complications we have not yet so much as glimpsed. But it seems plain that we must either allow our government to monitor possible terrorist communications when they occur, or witness their consequences at our leisure.