Well right, you can't arrest any of them until you've identified the entire group. Otherwise the rest of the group will go into hiding. But if it looks like you've found the whole group, then pack them up and send them to Club Gitmo for an extended vacation (with culturally correct meals, ping pong, soccer, and volleyball.)
Great and they can fly coach in the back of a cold and windy C130 with the bay doors open preferably.
Ah, Fox says London police are evacuating a mosque. Let's hope they demolish it.