A U.S. federal appeals court has overturned the terrorism conviction of Salim Ahmed Hamdan, a former driver for Osama Bin Laden.
In Tuesday's unanimous ruling, the three-judge panel said material support for terrorism was not a crime under international law at the time of Hamdan's conviction.
Hamdan was convicted by an a military tribunal at the U.S. military base in Guantanamo Bay, Cuba, and sentenced to 5 1/2 years in prison in connection to the September 11, 2001 attacks on the United States.
He was transferred to his native Yemen in late 2008 after receiving credit for time served. Yemeni authorities released him from prison in January 2009.
Meanwhile, a military tribunal at Guantanamo Bay began pre-trial hearings Monday for five alleged terrorists accused of conspiring in the 9/11 attacks.
Khalid Sheikh Mohammed, the self-proclaimed mastermind of the attacks, and four co-defendants face charges of terrorism, conspiracy and nearly 3,000 counts of murder, one for each known victim of the attacks on the U.S., including New York's World Trade Center and the Pentagon near Washington.