Indeed most experts in the field agree that the situation is, legally speaking, quite straightforward. Faced with terrorists, states can either class them as warriors, who would then be held as prisoners of war, with all the Geneva protections. Or they can decide they are criminals, to be treated by the normal process of law. Even the men picked up in Afghanistan, and now rotting in Guantánamo, could have been placed in either of these categories, rather than held to constitute a whole new category - "unlawful combatants" - and then duly plunged into a legal black hole.
The proto-fascists of New Labour seem to be creeping alarmingly quickly towards crypto-fascism.