WASHINGTON — Speeding through arguments in front of the Supreme Court, Attorney General Mukasey didn’t let time hang heavy on his hands yesterday.

The terse attorney general brought his first and likely his only case to the nation’s high court, asking justices to reinstate a dropped explosives charge against convicted terrorist Ahmed Ressam. At issue was whether the would-be bomber should be sentenced to 10 years in prison for carrying explosives in his car as part of his penalty for lying to American border agents in December 1999.

Several skeptical justices indicated that linking two potentially unrelated offenses amounted to a legal stretch.

“Could Congress pass a law that said if you wear a wristwatch during the commission of any crime, you get another 10 years?” Justice Antonin Scalia asked.

Mr. Mukasey scoffed at Justice Scalia’s extreme example.

“A statute like that would be entirely unreasonable,” the attorney general said.

Pressing the point, Justice Scalia said, “Surely it depends on what the felony is. If the felony is the filing of a dishonest tax return and you have a can of gasoline with you when you mail the letter, it seems to me quite as absurd as saying wearing a wristwatch in the course of a felony. That’s what troubles me about this.”

In all, however, Mr. Mukasey received a generally gentle hearing from the demanding court, to whom he outlined the government’s case crisply and with more confidence than he usually has with Congress or the press, whipping through his arguments in about 19 minutes.