"I should address the argument that Mr Hicks could have been charged with offences under Australian law. The best legal minds at the Government's disposal remain adamant that is not the case. That decision is more complicated than simply identifying a criminal offence. The likelihood of success, available defences, the facts in question and the rules of evidence in Australian courts must all be considered."
What that appears to mean is that Hicks can't be tried in Australia not because he couldn't be charged with a criminal offence but because if he was charged he would probably be found not guilty. He can't be tried in Australia because "the facts in question" won't convict him. To put it another way, we can't try Hicks here because the government believes he's innocent.