Well, I can read simple English...Well again Jim, you seem better clued in than the two Aussie governments who have handled Hick's case, I'm sure your skills woudl be appreciated here!
So unless they relied on someone with the reading comprehension skills of rubato to figure out the meaning of the relevant law for them, the decision has to have been political.
I know you have no difficulty believing that the US government is willing to offer other explanations in order to conceal political motives, do you not believe that Australian governments are similarly capable?
In fact in this case, again, given the known facts absent any evidence related to Gitmo, and the wording of the law, I don't think they even did a particularly good job of concealing the fact that the decision was political.
But apparently they did an excellent job of telling some people what they wanted to hear....
Which is something politicians are good at.
ETA:
If they claimed they couldn't prosecute the case because they couldn't use the evidence obtained at Gitmo, (which is what it looks like they did, based on what you've cited) they're either idiots, (given the fact that a person with very limited access to the relevant information and little time to devote to it was able to show clearly that such evidence was not needed to prosecute, given the wording of the law) or liars.
They have to be. (And I sincerely doubt that they are idiots)
In fact I think they were quite smart about it. They told the public they couldn't prosecute for reasons that the public was ready to believe without question because it focused on Big Bad Gitmo, and thus were able to avoid the political headache of putting him on trial.
Shame on them.


