Can I dump in the curbside sewer?

I think there are 2 issues at stake that are more important than the type of water involved. First, I'm 99% sure it is illegal. Second, what would your neighbors think? The black tank and gray water tank both empty out of the same trailer connection using the same stinky slinky. Your neighbor isn't going to know which you're dumping, and probably won't even know there is a difference in gray and black water. As far as they would be concerned, you're dumping your sewage into the storm drain.

It just seems like a VERY bad idea.