When the police see someone driving around breaking the law, it's their job to stop them.
But upholding laws on the road isn't a one-way street.
Gavin Seim turned the tables on a Washington state police officer in a video posted to YouTube last week, stopping the officer as the cop was driving an unmarked vehicle.
"Hey the reason I stopped you is I saw this car was unmarked," Seim asks the officer. "Is this a registered unmarked vehicle for undercover work?"
When the officer said it was a patrol car, Seim whipped out his legal knowledge.
"OK, you're not allowed to have patrol cars that are unmarked, are you aware of that?" he said, before citing the relevant law.