Mukasey was confirmed as attorney general last year. The nation's top law enforcement official traditionally makes at least one appearance before the high court during his or her term, usually in what's considered a "slam dunk" case for the government.
But none of Mukasey's predecessors in the Bush administration followed that tradition.
In the case before the justices, a trial court had found Ahmed Ressam guilty of conspiracy to use explosives at Los Angeles International Airport shortly before New Year's 2000. Ressam had been trained in Afghanistan by al-Qaida. The explosives were discovered in his car when he and another man crossed into Washington state from Canada on a ferry. He was sentenced to 22 years in 2005.
When an appeals court threw out one of the 10 charges against him on technical grounds, the government asked the Supreme Court for review.
Tuesday, Mukasey was loose and relaxed, but used only 19 of the 30 minutes alloted for his argument and answered some questions from the bench with a "yes" or "no," CNN reported. The justices did not press him very hard, the report said.
A decision in the case should come before the end of June.
(No. 07-455, U.S. vs. Ressam)