Does BSL work?

BSL has never been shown to reduce dog bites in a community. When BSL supporters point to a community where bites supposedly decrease, it is generally because other best practices were put in place around the same time. There are many reasons why BSL is a bad idea.

There isn't an objective way to identify breed
Most dogs in our community are mixed breed, or of unknown parentage. We often guess at heir breed because it appeals to our desire for labels and we feel that it might give us insight into their personality. Science tells us that most of the time, our breed guesses are incorrect. 

DNA tests have become popular, but for mixed breeds their accuracy is unknown. Despite the popularity of these testing kits, the companies who make them are not eager to share their research on accuracy. They have stated that for purebred dogs, and for some first generation mixes (both parents are purebred) the accuracy rates may be as high as 80-90%. For the rest of dogs, who constitute the majority in our population, the accuracy rate would be much lower.

Breed doesn't guarantee behaviour
Studies have identified risk for dog aggression. Breed is not one of them.

The genes that make up physical characteristics (pointy nose, long ears) are not associated with the genes for intelligence or temperament. A dog that looks like breed is not guaranteed to act like that breed.

Breed traits do exist, but breeders work very hard to cultivate this consistency across generations. In each litter there are differences between individual puppies, and despite their genetics not all will conform to a breed standard.

With most dogs in our community, it's unlikely that they have generations of consistent breeding in their pedigree. Most likely they are bred by accident, by a casual breeder, or perhaps by a backyard breeder or puppy mill. Whatever they may look like, we can only assume one thing about their personality: they are an individual, and should be evaluated as such.

BSL is expensive
Enforcing laws based on appearance requires extra resources. It means that animal control resources are spent chasing down dogs that look a certain way, rather than owners and dogs that are actually causing trouble in the community.

In jurisdictions with breed bans, dogs are seized, impounded, and subject to court cases to decide their fate - not because they have demonstrated a risk to their community, but because lawyers and professionals are required to spend their time deciding if the dog meets a visual criteria.

Restricted dogs are more likely to end up in the shelter system because they are discriminated against. Because of the restrictions required to own them, they are slow to be adopted and the City will need to pay for their care.

It doesn't stop "undesirable" owners
BSL if often touted as a way to keep aggressive dogs out of the hands of criminals. There's no evidence that it works this way. Irresponsible owners won't hesitate to get an "illegal" dog and if that one is taken away, there are plenty other large, strong breeds that they can choose from, and the outcome is the same.