Australian David Hicks is one step closer to having his conviction as a war criminal quashed, after a US court found the offence he pleaded guilty to was not a war crime.

After being captured on the Afghanistan battlefield and spending six years at Guantanamo Bay, Hicks entered a plea bargain in March 2007 before a US military commission to a charge of "material support for terrorism".



In a separate case, all seven judges of the US court of appeals for the DC circuit have now found that charge is not a war crime triable by military commission.



Hicks's appeal against his conviction before the court of military commission review had been stayed pending the outcome of the DC appeal court in the case of Ali Hamza al-Bahlul, who had been Osama Bin Laden's PR man. A charge of conspiracy against al-Bahlul has been upheld.



Hicks was accused of materially supporting terrorism by "engaging in combat" against US forces in Afghanistan.



The offence was created by Congress after Hicks allegedly committed it – material support for terrorism had never been a war crime before the establishment of the military commissions.



In 2009 lawyers from the US Department of Justice told Congress "material support for terrorism" was not a valid war crime and should be dropped from the Military Commissions Act.



But Congress failed to remove the offence from the act and the Obama administration accepted a guilty plea for the offence from Ibrahim Al Qosi, bin Laden's cook and bookkeeper.



This latest finding further weakens the military commission apparatus on Guantanamo.



Since the detention centre was set up only eight prisoners have been convicted of war crimes. Six were the result of plea bargains (including Hicks) and another case was overturned by a civilian court.



Six more are in the process of being tried, including five accused of organising the attacks of 11 September 2001. Hicks was the first Guantanamo prisoner to be convicted of an alleged war crime.



The Australian maintained his innocence, but accepted that the prosecution's evidence would be likely to convict him.



Colonel Morris Davis, the Pentagon's chief prosecutor at the military commissions, said that the process in Hicks's case had been flawed and driven by the Bush administration for the political benefit of John Howard’s government, which had painted Hicks as a terrorist.



After he was released from Guantanamo Bay the plea deal required him to spend nine months of a suspended seven-year sentence in South Australia's Yatala prison. He was prevented from speaking to the media and waived his right to appeal. His defence team failed to file the waiver, so that part of the plea deal became null.



The government delayed Hicks’s release until after the 2007 election. Thereafter he was placed on a control order that had been obtained by the AFP. He could not leave Australia, had to report to the police three times a week, and could only use an AFP-approved mobile phone SIM card.



The control order expired in December 2008.



The Liberal senator George Brandis continued to campaign against Hicks from the opposition benches and urged the Commonwealth director of public prosecutions to bring a proceeds of crime case in relation to the publication of Hicks’s book Guantanamo: My Journey.



In 2012 the DPP withdrew the case after it was pointed out that admissions of guilt were inadmissible if they had been procured by "violent, oppressive, inhuman or degrading conduct".



Hicks maintained he had been subject to all those abuses at Guantanamo Bay and pleaded guilty only in order to be released from US custody.



This article was amended on 17 July 2014. In the original version, it was stated that it was the prosecution (rather than Hicks' defence team) that failed to lodge a waiver.