Unconstitutional

Via the International Herald Tribune - U.S. court deals a setback to Guantánamo prisoners

The article is about the ruling of the U.S. Court of Appeals for the District of Columbia Circuit that said detainees can no longer sue in federal courts and the appeal that is being planned. One statement in the article struck me as odd:

Attorneys argued that the detainees were not covered by that provision and that the law was unconstitutional.

"The arguments are creative but not cogent," Judge A. Raymond Randolph wrote. "To accept them would be to defy the will of Congress."

What strikes me as odd is that "defy the will of Congress" statement. Isn't that what the Supreme Court is ALWAYS doing when it finds a law unconstitutional? I mean, what kind of argument is that?