Because if You Try Them In Federal Court, They Will Just

Plead guilty and cooperate with authorities and provide intelligence:

Terror suspect Najibullah Zazi, an immigrant from Afghanistan who was living in Denver, has admitted he planned to try to set off explosives to kill Americans, most likely in New York.

He also pleaded guilty to conspiracy to commit murder in a foreign country and providing material support to a terrorist organization.

His guilty plea may mean even more for the war on terror, since it appears Mr. Zazi has agreed to cooperate with federal officials.

Should have waterboarded him, that would have shut him up.