[JURIST] The US Court of Appeals for the District of Columbia Circuit [official website] on Tuesday vacated [opinion, PDF] the conviction of Salim Ahmed Hamdan [DOD materials; JURIST news archive], Osama bin Laden’s former driver. Hamdan was convicted of conspiracy and material support for terrorism under the Military Commissions Act of 2006 [materials, PDF]. At issue in the case was whether the Military Commissions Act applied to Hamdan’s conduct from 1996-2001. If not, the court examined whether his conduct constituted a war crime under the pre-existing military commissions statute. The appeals court held that because the Military Commissions Act does not retroactively punish new crimes, and because material support for terrorism was not a pre-existing war crime at the time of his conduct, his conviction must be vacated. The court held:

To avoid the prospect of an Ex Post Facto Clause violation, we interpret the Military Commissions Act of 2006 so that it does not authorize retroactive prosecution for conduct committed before enactment of that Act unless the conduct was already prohibited under existing US law as a war crime triable by military commission. In this case, therefore, Hamdan’s conviction stands or falls on whether his conduct was prohibited by the pre-existing statute 10 USC § 821, at the time he committed the conduct…Material support for terrorism was not a war crime under the law of war referenced in 10 USC § 821 at the time of Hamdan’s conduct.

Additionally, the court held that Hamdan’s direct appeal of his conviction was not mooted by his release from custody.

In June the DC Circuit ordered [JURIST report] attorneys in the case of the former Guantanamo Bay [JURIST backgrounder] detainee to supply briefs explaining whether the issue has become moot because Hamdan already completed his sentence and is no longer living in the US. In a post-argument brief, lawyers for Hamdan argued that his conviction will continue to have adverse affects on his life, including his permanent ban on travel to the US and potential future political conflict with US army, which continues to occupy his home country of Yemen. Following the Authorization for Use of Military Force [text] (AUMF) against those responsible for the 9/11 attacks, Hamdan was captured in Afghanistan while driving in a vehicle that contained two anti-aircraft missiles. He was then transferred to Guantanamo Bay, Cuba where the US Military detained him and, at a military tribunal, charged him as an unlawful enemy combatant who had committed war crimes. Hamdan challenged his conviction, prompting a decision from the US Supreme Court [official website], which held [opinion; JURIST report] that his trial violated US and international law. Congress subsequently passed the Military Commissions Act of 2006 and Hamdan was convicted [JURIST report] yet again. Hamdan’s conviction was affirmed [JURIST report] by a US Court of Military Commission Review [official website], prompting an appeal to the DC Circuit Court of Appeals and ultimately resulting in Tuesday’s decision.