If cops ask for a permit and they don't have one, they'll be arrested on the spot...this is NYC, I lived there for years....the cops are just folks, they can party like you wouldn't believe, but they take nothing from anyone.
It may not be right, but they ain't afraid to take you out back and re aquaint you with Mr. "respect law and order" and it can really make you ask yourself if it's worth it to continue.....
and some of them are Union thugs too, so they have some real experience.