"We are hoping that the military commission will make a ruling within a month," Hicks' lawyer, Stephen Kenny, told the Sydney Morning Herald.
US civilian courts previously ruled that the crime he was charged with does not apply to actions committed before 2006, according to the BBC.
Captured in Afghanistan in December 2001, Hicks admitted to being trained in Taliban camps, but did not see evidence of terrorist activity, according to Reuters.
However, Hicks' lawyers say that his confession was made under duress, and that he was suicidal and desperate to leave the controversial prison, according to the BBC.
The Guantanamo Bay detention facility was opened in 2002 in the wake of 9/11 terror attacks on the United States. Since then, the prison has been repeatedly criticized by human rights advocates citing inhumane conditions of confinement, including torture.