WASHINGTON (AFP) - A US appeals court overturned the war crimes conviction Friday of an Al-Qaeda propagandist, a ruling that could lead authorities to drop conspiracy charges against the five 9/11 plotters.
The US Court of Appeals in Washington threw out the conviction of Ali Hamza al-Bahlul on the basis that the charges he faced were not recognized as war crimes under international law when the events took place.
The Yemeni prisoner has been held at the US facility at Guantanamo Bay, where he was facing life in prison after being convicted in 2008 on charges of conspiracy, providing material support for terrorism and soliciting murder.
In October, the same court threw out the Guantanamo conviction of Osama bin Laden's driver Salim Hamdan on similar grounds.
It said a law that listed material support for terrorism as a war crime -- approved in 2006 in response to Hamdan's case -- could not apply to him retroactively.
Mr Bahlul was alleged to have created propaganda videos for Al-Qaeda in which attacks against the United States were glorified.
Following the Hamdan ruling and in anticipation of the decision in Mr Bahlul's case, the chief prosecutor at Guantanamo, Brigadier General Mark Martins, had asked the Pentagon authority overseeing the trial to drop the conspiracy charge against the men accused of plotting the Sept 11 attacks.
But the request was rejected by the Convening Authority that has oversight of the US military prison based in Cuba.
President Barack Obama's administration can appeal the latest ruling to the US Supreme Court or try Bahlul once more before a military commissions tribunal at Guantanamo.
Mr James Connell, a defense lawyer for 9/11 defendant Ali Abd al-Aziz Ali, said the decision was "important" because the court "held that conspiracy was not a war crime that can be tried by a military commission".
"The detainees in Guantanamo convicted for conspiracy can have their conviction vacated," he added.
Another former Guantanamo detainee, Australian David Hicks, is asking for his conviction to be revised after the Hamdan ruling, even though he has already returned to Australia.
Mr Connell said Gen Martins's request to drop conspiracy charges against the 9/11 plotters should be examined during the next preliminary hearing for the accused, which is expected in April.
Another preliminary hearing set to begin on Monday at Guantanamo will focus on CIA secret prisons, where the five men were held and interrogated -- at times with techniques that critics consider torture -- before being transferred to Guantanamo in 2002.
Khalid Sheikh Mohammed, the self-proclaimed mastermind of 9/11, and his four alleged co-plotters stand accused of eight charges, including conspiracy, in connection with the deadly airliner attacks in the United States in 2001.