Mr Hicks has been held in a US military facility at Guantanamo Bay in Cuba since his capture in Afghanistan in late 2001 where he was allegedly fighting with the Taliban.
The Fair Go For David group in the South Australian capital of Adelaide said this weekend marked his fourth year in detention, despite inconclusive evidence about his activities.
Group spokeswoman Tasia Pertsinidis said it was important the charges against Mr Hicks were tested in a civil court.
"Providing David Hicks with a fair court trial is of paramount importance," she said.
"It will provide lawyers the opportunity to achieve justice and a fair go for David."
Mr Hicks is still expected to be the first of nine US detainees to face trial by special military commissions, which have been strongly condemned by civil libertarians and even many of the military lawyers defending the detainees.
Those commissions have since been put on hold by action in the US courts.
Mr Hicks has pleaded not guilty to charges of conspiracy to commit war crimes, attempted murder and aiding the enemy.