The justices declined to hear Ali Hamza al Bahlul's appeal of a lower court's ruling rejecting his claim that the military commission set up to deal with war crimes that convicted him in 2008 lacked the authority to prosecute him for the crime of conspiracy. Under international law, conspiracy is not considered a war crime, his lawyers had argued.

Bahlul, who made videos as part of his work for late al Qaeda leader Osama bin Laden's organization, was captured in Pakistan three months after the Sept. 11, 2001, attacks on the United States and was transferred to Guantanamo Bay.

A military commission convicted him of three crimes — conspiracy, providing material support for terrorism and solicitation of others to commit war crimes — and sentenced him to life in prison. A federal appeals court in 2014 threw out his convictions on all but the conspiracy charge.