Avengers house
Inside or somewhere well away from the public is fine. I'm pretty sure I'm grounded though, even at night and away from the town there's too much chance of being seen. If there's a threat, yeah, it gets tricky, and that's one of the things we're going to want to find out. It might end up being a subjective judgement call on their part, which means it should be an extreme situation, aiming to contain rather than harm if possible, fully cooperating afterwards... and honestly it would probably go better for the nice white people than anyone who looks at all different or scary.