That's exactly the problem. If other people "see" the dog as being pitbull (or any other restricted breed), then how do you prove otherwise? Your dog can be confiscated under a law, denied coverage under the insurance, kicked out of an RV park, etc., based on appearance - regardless of the actual truth of registry.
Growing up, I had a purebred boxer. She was a rescue, so there were no papers proving her breed. She was a very "poor" boxer - her nose too short, her body too squat, solid white, etc. This was in the days that pitbulls were just starting to get a bad rap but it wasn't widespread. She was the sweetest dog that our family EVER owned. She had pet rats, newborn kittens, macaws, and babies/toddlers crawl all over her and she'd just lay there completely still.
Today, she'd be impounded as a pitbull under these breed restrictions and there'd be no way to prove she wasn't a pitbull.
That is why breed restrictions are wrong and fail.
