The Court’s decision was largely based on the ‘ex post facto’ legal principle, which ensures that defendants are not charged retroactively with crimes – a point argued by Hicks’ lawyer Dan Mori in 2007.

Hamdan was convicted for conduct committed when he worked for al-Qaeda from 1996 to 2001, several years prior to the enactment of the 2006 Military Commissions Act under which he was charged.

Like Hamdan, Hicks was charged with “material support for terrorism” under the 2006 Act, even though it was in 2001 that he allegedly “engaged in combat against US forces” in Afghanistan.

“The issue of retrospectivity in the Hicks case is blatant,” ALHR president Stephen Keim (pictured) told Lawyers Weekly.

War criminals convicted at the Nuremburg trials in Germany were also, for the most part, prosecuted under retroactive law. But the Hicks case is different, said Keim.

The actions of those tried at Nuremburg were criminal even though they were not in breach of international law, he argued. But in the Hicks case, military commissions “turned behaviour that was ambiguous, not considered criminal under any jurisdiction, into a crime”.

“[Hicks’ conviction] is a black mark on our moral history and that of the US.”

Keim doubts, however, that Hicks can obtain redress from the Australian Government. If his certificate of conviction is deemed invalid, Hicks will still struggle to seek damages for wrongful imprisonment because he wasn’t convicted under Australian law.

Another obstacle is the plea deal he entered in 2007, which included a commitment not to challenge his conviction.

“It’s difficult if you’ve entered a guilty plea to be able to say afterwards that it should be set aside ... it’s unclear and may require further litigation to be contested,” said Keim

Even if his plea is overturned on the basis that the crime was non-existent, Keim pointed out that Hicks was not charged for most of his detention in Guantanamo Bay. He was held pursuant to a 2001 resolution passed by US Congress authorising the use of military force by the government against those responsible for the September 11 terrorist attacks.

However, this excludes the nine months he spent in an Adelaide prison in 2007 after he was charged and convicted.

Earlier this year, the director of public prosecutions dropped its application to prevent Hicks making money from his memoir, Guantanamo: My Journey, after it had tried to claim that the profits of the book were the proceeds of a crime.

But Keim said the decision in the memoir case, which found his guilty plea was obtained under duress, can’t be used to support a damages claim against the Government, reiterating that the Hamdan decision, on which the damages claim hinges, is a matter of US domestic law.