Ball mounts Is it legal to have one when not towing?

One of those things that may, some day, cause you an issue. In this day and age of lawyers suing for everything and nothing being the idiots fault, it is just a matter of time until a regular Joe with his hitch in his truck loses everything because the rich guy in a sports car doing 140 mph slid sideways into the back of his truck putting the hitch into the passenger compartment. I would guess it has happened in the past. That said. My hitch is usually in place.