What are they going to do? Surround us with riot police? Encase us in some Roman ensemble of police?
Can't see it personally, it'll be a shit show and no one will pay any attention to it. If they actively try and treat it like some enforced bubble they'll only end up getting people's backs up and creating a toxic atmosphere, and that'll lead to confrontation and everyone fucking it off anyway.
Can you see anyone sticking around when all their pals will be having it in Porto all day having a proper day of it? Destined to fail IMO.