Ever hear of "reading someone the Riot Act"??? Well, that's a real thing. There used to be (and perhaps still is) on the books an actual "riot act," in which the state or locality in question reserved the right of its officers to utilize deadly force against rioters. What would happen is that if a "peaceful protest" was getting out of hand, some officer would appear and read off the riot act to the crowd - as in, "Under the riot act we can shoot you dead. If you don't clear the streets in 5 minutes, we're going to start doing that." Almost all of the time - after the first time - the streets were cleared in 5 minutes, pretty much anywhere that this was done.
We need that put back into practice - preferably with these: