Breed specific legislation is any government law, rule or regulation that applies only to certain breeds of dogs, or discriminates against certain dogs based on their breeds. Such laws usually target breeds that have a stereotype of being dangerous, such as Rottweilers, Presa Canarios, or "pit bulls." Pit bulls are actually three different breeds: the American pit bull terrier, the American Staffordshire terrier and the Staffordshire bull terrier.
Breed specific legislation might require an additional registration fee for certain breeds of dogs, requires the dogs to be muzzled in public, or completely forbids the keeping of those dogs.
Animal activists object to breed specific legislation because it is based on stereotypes of certain dog breeds, and has nothing to do with whether a particular dog is dangerous or vicious. Tests by the American Temperament Testing Society show that collies, toy poodles, or beagles are all more aggressive than the three "pit bull" breeds. These laws foster irrational fears and lead to animals being abandoned.
Also, breed specific legislation does nothing to address the real problem - irresponsible people, and has proven ineffective in protecting public safety. Laws already address issues like dog bites, leashes and stray animals, so there is no reason to have another law that tries to address the same issues but puts innocent animals at risk.
A popular slogan among anti-BSL activists is "Punish the deed, not the breed." The point of the slogan is that each dog should be judged as an individual, regardless of breed.