In an en banc decision, the U.S. Court of Appeals for the District of Columbia vacated two of the three guilty verdicts against Ali Hamza al Bahlul. He was convicted in 2008 of conspiracy in war crimes, the only charge to stand, and of providing material support for terrorism and recruiting others for war crimes.
"Solicitation of others to commit war crimes is plainly not an offense traditionally triable by military commission," Judge Karen LeCraft Henderson wrote. "The government offers little domestic precedent to support the notion that material support or a sufficiently analogous offense has historically been triable by military commission."
Three judges released opinions that dissented in part from Henderson's decision.
Bahlul refused to participate in the 2008 proceedings. A three-judge panel ruled for him but the government asked for a hearing before the entire court, known as an en banc proceeding.
The military commission sentenced Bahlul to life in prison in 2008, and he is currently the only life-sentenced prisoner held at Guantanamo. The appellate decision could mean a new sentencing hearing.
Bahlul traveled from Yemen to Afghanistan in the 1990s to join al-Qaida. He was captured soon after the 2001 terrorist attacks and has been at Guantanamo for more than a decade.