Zacarias Moussaoui deserved to die far more than any of the innocent victims of 9/11. Instead, he was tried in a civilian court and sentenced to live a long and healthy life at taxpayer expense, if not a comfortable one. As far as I'm concerned, the minute he said, "I am a member of al-Qaeda," he should have been taken out back and shot without another word. Unfortunately, membership in an organisation dedicated to the deliberate mass murder of innocent people in order to enslave the world under a twisted religious dictatorship doesn't happen to be grounds for immediate execution. Meanwhile, French Foreign Ministry spokesman Jean-Baptiste Mattei has already spoken of a "possible demand for transferring Zacarias Moussaoui" to France. That's what happens when we treat terrorism as a matter of law enforcement rather than an act of war.

In June 1942, eight German agents entered the United States in two groups of four, landing by submarine in Florida and New York. They carried "enough explosives, primers, and incendiaries to support an expected two-year career in the sabotage of American defense-related production." George John Dasch, the leader of one group, apparently lost his nerve. He called the FBI and surrendered. Dasch convinced another man, Ernest Peter Burger, to talk to the FBI as well. Because of the information they gave under interrogation, the others were rounded up within days.

The eight saboteurs were tried before a military tribunal and sentenced to death. In ex parte Quirin, the Supreme Court decided that the eight men had violated the rules of war by wearing civilian clothing during a military operation. President Roosevelt commuted Dasch's sentence to 30 years and Burger's to life imprisonment. The other six were executed within a few days of sentencing. They never got a chance to commit even a single act of sabotage. The Nazis were so stunned by the utter failure that they never tried another such operation. That's the proper way to handle enemy agents in a time of war.

Moussaoui, on the other hand, was sent through our criminal justice system. He had foreknowledge of a terrorist act that cost the lives of nearly 3,000 innocents. He confessed that he had planned to fly a plane into the White House in a separate operation. He was in FBI custody before 9/11, yet deliberately lied to prevent anyone from discovering the plot before the attack took place. As an agent of a foreign power intent on committing terrorist acts in the US, surely he deserved the same fate as those long-dead Nazi agents who only planned to blow up defense installations. But because he was tried by a civilian court instead of a military tribunal, Moussaoui was allowed to live.

We've all heard the reasons for not sentencing Moussaoui to death. "He had a rough childhood" is one of my favorites. Lots of people have rough childhoods; it's no excuse for becoming a terrorist. "He didn't actually kill anyone" is another. Neither did those Nazi saboteurs; the only crimes they actually committed were immigration violation and conspiracy. There's also the smug "he wanted to die, and we denied him his wish." Next time I get stopped for speeding, I'm going to tell the cop that I really want a ticket, and the best punishment would be to deny me my wish. Maybe I can get away while he's laughing.

Some might think that by showing "mercy" to Moussaoui, we've made some sort of point with either our enemies or our allies. A trial is supposed to be about law and justice. Sometimes it's about retribution and punishment. One thing a trial should never be is a world popularity contest. Our allies don't need to be reminded who we are and what we stand for, and there isn't a single enemy who will think, "Gee, maybe the Great Satan isn't so bad after all." On the contrary, we've shown the world that we don't take this war seriously by allowing Moussaoui to live.

Our enemies will take the Moussaoui sentence as a sign of the same weakness of will that led them to plan 9/11 in the first place, and maybe they have a point. We treated terrorism as a law enforcement problem all through the nineties, while our enemies were at war with us. The response to the 1993 World Trade Center bombing, for instance, was a trial. Few dared to look beyond the immediate perpetrators to seek those who sent them. The entire fiction of "stateless terrorism" was created just to avoid confrontation with Iraq over the bombing.

Ramzi Yousef, the "mastermind" of the 1993 bombing, sits in the same Supermax prison for which Moussaoui is destined. Did Yousef's trial and incarceration stop our enemies, the way executing Nazi saboteurs did? On the contrary, Bin Laden and his kind saw that we arbitrarily bound ourselves in ways that gave them freedom to act, and let them take the initiative against us. They saw that we would not act without clear evidence and court orders. Yousef got to watch 9/11 unfold in his cell while reading his Qur'an. What future attacks might Moussaoui get to witness?

War has different rules than catching crooks, for obvious reasons. Common criminals generally aren't trying to destroy our civilisation; they're trying to live off it. Soldiers on a battlefield don't have to collect evidence or conduct a trial before shooting an enemy. But in this kind of war, the battlefield is everywhere, and enemies hide among our own people. Captured enemies should be brought before a military tribunal and executed without long delays. If we return to the law enforcement mindset when dealing with terrorists, we return to the sort of willful blindness that let our enemies plot to kill thousands.

One can only hope that we learn a lesson from this whole Moussaoui trial: civilian criminals are one thing, and enemies another.