Do you know this from personal experience?
He followed me from a student housing complex for several blocks before "hitting the blues", when I had stopped at another apartment complex to make a delivery.
As I returned to the truck, I muttered to myself "What's this a$$h*le going to do, give me a parking ticket?"
When he finally asked me "Do you know why I pulled you over", I looked him in the eye and said, "No, not really!"
He proceeded to tell me that because my son (aged 12 at the time) was with me, and the door was open, that he was in danger of falling out and getting hurt.
I asked him if there was a law concerning it, he said no.
I snatched my license from his hand, bid him goodbye and went about my business....