Like, here when protesters throw bricks and shit, which is rare, the police announce that if you're in the vicinity of those people and happen to look like them, you risk getting taken in temporarily. Last time came a law that it's now illegal to cover your face at protests, cos it shows your intentions.
I even know people who was in the last of those incidents as non-aggressors and got taken in. We had fun about her experience actually.
We have an old and proud protest tradition that needs approval by police, like time, place and protest direction to keep it orderly. Even a yearly symbolic political tradition for the left for decades
Damn, I'm rambling...