The Wall Street Journal exposes the weakness of the "imminence argument."

All of this is simply an invention after the fact, and a dangerous one. President Bush did use the word "imminent" once in this year's State of the Union, but precisely to rebut the standard Mr. Wilson now wants to claim as the standard for American self-defense. "Some have said we must not act until the threat is imminent," Mr. Bush said, but he then rejected that test. "Since when have terrorists and tyrants announced their intentions, politely putting us on notice before they strike?"

....The larger trouble with the imminence threshold is that in a post-September 11 world it is impossible to define and is therefore dangerous. When can we really say that the World Trade Center attack was "imminent?" Perhaps even Senator Graham would agree it was imminent on September 10, when the killers partied away in Portland, Maine, but of course by then it was too late to stop it except by luck.