FORMER Prime Minister John Howard has refused to apologise to David Hicks, after the former Guantanamo Bay inmate won an appeal to quash a terrorism conviction against him.

Mr Hicks won the appeal in the United States Court of Military Commission yesterday, with the court striking down the 2007 conviction.

His Australian lawyer Stephen Kenny reportedly said it was a declaration that Mr Hicks was "an innocent man".

But Mr Howard said Mr Hicks was not owed an apology over the conviction as it was a US court matter, not an Australian case.

He said nothing altered the fact Mr Hicks had trained with al-Qaeda and "revelled in jihad".

But Greens leader Christine Milne told reporters in Adelaide he was owed an apology by Mr Howard, for "failing to stand up to the Americans".

Mr Hicks was held for five years in the offshore prison.