David Hicks' conviction at Guantanamo Bay in 2007 has been ruled invalid by a US appeals court, paving the way for a full vindication of his innocence.
The Washington DC federal appeals court found that the charge of providing material support for terrorism against three men, including Osama bin Laden's former driver Salim Hamdan and Mr Hicks, could not be applied retrospectively.
The charge was created in 2006.
Mr Hicks was controversially detained on the charge at Guantanamo Bay from 2001 until 2007.
The chief prosecutor in the Guantanamo Bay military commissions in 2008, Col. Morris Davis (Ret.), told a US publication that the finding was “a body blow to credibility of the already beleaguered military commissions".
“I was one of the advocates for adding material support as a chargeable offense when Congress was crafting the Military Commissions Act in the summer of 2006. I personally approved the material support charges against Hamdan and Hicks in February of 2007. I realized later on that I was mistaken on both counts,” Col. Morris Davis said.
Mr Hicks' former millitary lawyer Dan Mori told ABC24 it was vindicating “to have a US Federal court say you were right all along,”
Mr Mori said he expects the Australian government to respond given the complicity in the two government's cooperation to convict Mr Hicks.
“The validity that these aren't a valid offence and knowing that he was treated inappropriately, hopefully there will be some closer with the government,” he said.