I'm referring to clear, unambiguous riots, where people run around looting stores or burning buildings down. Misuse of the American legal definition is a separate issue, and not one I'm interested in discussing.
I've seen plenty of events here in the Pacific Northwest that police have labelled riots that I would in no way call a riot. I think that the legal definition very much plays into the discussion, because it gives the police the power to tell the media that a riot occurred.
Something that happened here, as the protests kicked up, was organized robbery under the guise of looting. We'd see a van pull up to a boutique clothing/electronics store, and a group would pour out... a mix of "looters", lookouts, and security. They'd smash the store, grab the best stuff, toss it into the van, and roll away in minutes. That's not "looting". That's organized crime. And, because Minneapolis police were too busy tear-gassing peaceful protesters to bother protecting residents or property, it was easy.
So Chicago... after a police shooting, someone immediately goes online and calls for looting downtown, where all the nice boutiques are. Which, of course, creates plenty of cover for these organized teams to clean out stores. In other words, there's a fundamental difference between an organized crew robbing a boutique clothing store, and a poor mother walking out of a "looted" Target with a grocery cart full of diapers and food.
The public conversation, of course, lacks such distinctions.
The protesters were in open communication with police and city officials. The protest was peaceful, the police did not start a fight, and neither did the protesters. The protest peacefully dispersed later in the evening.
Meanwhile, a few blocks away, what some might describe as a gang did a smash-and-grab at the (closed) Bellevue Square mall, grabbing merchandise off the store shelves, loading it into cars, and fleeing.
If the police wanted to pick a fight, they would have declared the situation a riot, and opened fire on protesters. They didn't, though.
It's one that's applied in practice, as justification for police violence, over and over again.
In practice, a lot of the time, peaceful protests turn into 'clear, unambiguous riots' after police violence starts. Generally speaking, protesters try to police themselves - but when you're half-blind, stumbling away from clouds of teargas, you aren't going to do anything to stop the idiots who took advantage of the chaos to start throwing bricks at store windows.