Uh, you are talking about two drastically different things.

1) Breed bans--making it illegal to own certain breeds.

2) Dangerous dogs being returned to families, regardless of breed.

The first has been proven to be ineffective. First, it's nearly impossible to identify mixes--and at what point is a mix considered the "dangerous" breed? If it is 25% pit, is it a pit? If it looks like a bully breed, is it "dangerous"? Second, take away one breed, and the scumballs will find a new breed to play with--or they'll own it anyway. If they are engaging in dog fights, they don't exactly concern themselves with legality.

The second is a legitimate issue. Dogs who are convicted of bites/attacks need to be on the dangerous dog registry (meaning there is a large fee paid each year, the dog has to be behind multiple barriers, cannot be in the vicinity of children, cannot be in public unmuzzled, etc), or put down. It will not be adopted out to an unknown stranger or shipped out of state.

After several personal experiences I became aware of breed specific legislation and policies of jurisdictions. Unfortunately advocates for some breeds have resulted in even dogs which kill or maim being potentially released back to owners. For example a dog responded to a cough by inflicting head wounds on it's owners 3 day old baby, it was ruled an accident, and the owner's have the option of reclaiming the dog. If they don't reclaim the dog what will happen? Adopted out to another individual? Move it out of state through rescue networks then adopt it out?

http://wtop.com/national/2016/04/autopsy-newborn-killed-by-dog-died-of-bites-to-head/