that because they haven't been tried these men can't be held in prison. They're considered a threat, so presumably they can't just be left to wander about the country as they like.
They'll presumably be subject to Control Orders, and that involves:
1. Electronic tagging 2. No passport 3. Living at one address 4. Curfews 5. Restrictions on visitors 6. No internet access 7. Attend only one place of worship 8. Daily reporting to the police 9. Daily monitoring by phone
I imagine it's an unpleasant regime, and it must cost quite a bit to administer. The Liberal democrats have previously been dead against Control orders