WASHINGTON - A US federal appeals court has overturned the terrorism conviction of Salim Ahmed Hamdan, a former driver for terror mastermind Osama bin Laden, who served a prison term for material support for terrorism.

In a 3-0 ruling, the court ruled that material support for terrorism was not an international-law war crime at the time Hamdan engaged in the activity for which he was convicted.

Judge Brett Kavanaugh of US Circuit Court of Appeals for the District of Columbia, wrote in the court's opinion that "when Hamdan committed the conduct in question, the international law of war proscribed a variety of war crimes, including forms of terrorism. At that time, however, the international law of war did not proscribe material support for terrorism as a war crime."

"We reverse the judgment of the Court of Military Commission Review and direct that Hamdan's conviction for material support for terrorism be vacated," said the opinion.

Hamdan, a Yemeni, was captured during the Afghanistan war and imprisoned at the US military prison facility in Guantanamo Bay. He admitted to being bin Laden's personal driver.

Hamdan, who was convicted by the military commission and sentenced to 5 and half years in prison, was given credit for time served and is back home in Yemen. Reports say he works as a taxi driver there.