Breed Specific Legislation (BSL) refers to laws or policies which are directed towards a single dog breed or a limited number of dog breeds, while other breeds are excluded from said law/policy. BSL mainly regulates breeding and owning of specific breeds, especially the so called "pitbull-type" dogs.
BSL came forth from the idea that the population should be protected from "aggressive" dog breeds. Characteristics that, in relation to BSL, are considered to be related to "aggressiveness" are, among others, jaw strength, and overall musculature.
Both are involved in the ability of a dog to cause harm to another being (for example a human, other dog or cat). Clearly, an attack by a dog with more powerful jaws will most likely aggravate the injury that is sustained per bite wound. Also, in general, "pitbull-type" dogs can be very dominant towards other dogs and are highly likely to win in a direct fight.
First, of all, one can question whether the characteristics that are evaluated for the determination of the aggressiveness of a dog breed are chosen well. Jaw strength and musculature are involved in the damage that results from a dog attack, however there is no evidence for a link to general aggressiveness.
Second, the concept that so-called pitbulls have stronger jaws than other breeds is not necessarily true. Although famous for their bite, other dog breeds can have equally powerful jaws. Some recent studies even point to stronger bites in various other popular breeds (e.g. Rottweiler). Also, the proposition that "pitbull-type" dogs are more muscular than other dogs is not generally true. They are among the strongest dogs for their size, but larger dog breeds can easily have by far more muscle mass and can thus impose a bigger danger to a human being. Even in their weight class they can be, and are in practice, beaten by other breeds in weight pulling competitions.
Third, it is not clear what a "pitbull-type" dog is exactly. More than ten different dog breeds have been given this notorious label, including bulldogs and boxers. There are many examples of negative press exposure of the "pit bull", where the dog involved in an attack belongs to a breed that is not a pit bull by any standards.
Fourth, "pitbull-type" dogs like the American Staffordshire Terrier (AST), the Dogo Argentino, and in particular the American Pit Bull Terrier (APBT) and the Staffordshire Bull Terrier (SBT) are human-friendly animals, when trained well they are less likely to attack someone than for example, a German Shepherd or Rottweiler (breeds that were also bred for alloofness to strangers and man-stopping instincts and abilities). A case has been known where a Dogo Argentino was stapled over 10 times by a child without an aggressive response, and the SBT is nicknamed "the nanny dog" in its land of origin due to itís trustworthy, child-friendly behaviour. This extreme friendliness to humans is a result of generation on generation of breeding for fighting capabilities under pit rules. Game-bred fighting dogs such as APBT are not aggressive to humans.
In contrary, when a fighting dog shows aggressiveness towards its handler (an individual that the dog is acquainted with), the handler of itís adversary (an individual the dog is unacquainted with) or the referee (an individual the dog is unacquainted with), who should all be able to stand next to the dog in the pit and if necessary even pick up or otherwise handle the dog while engaged in a fight, it is disqualified and excluded from the breeding program.
Their natural lack of aggressiveness to humans makes them less useful for those looking for a canine weapon. One should note that the Dogo Argentino, in contrary to staffords (especially APBT and SBT, and to some lesser extent also AST) had some purpose as a guard dog. The main purpose of the Dogo Argentino was that of a large game hunting dog and a second purpose was sometimes that of family guardian. Staffords are generally very inadequate dogs for the protection of property due to their human friendly nature.
Fifth, pit bulls are generally lightweight dogs bred for endurance and tenacity. A 200 pound Boerboel is far more likely to kill someone outright than the average 65 pound "pitbull" (here referring to the American Pit Bull Terrier, Staffordshire Bull Terriers are even lighter, weighing around 35 pounds). In general, the larger the dog, the bigger the risk it poses to man, especially in terms of fatalities.
Sixth, in areas where BSL is implemented, no effect on the dog attack incidence is observed. This might be due to the fact that nearly any dog can be turned into a weapon by those with bad intentions. When one breed is forbidden, one can easily find another. There are many dog breeds that pose a far larger threat to humans than the APBT, the SBT, the AST or the Bull Terrier, the four breeds most commonly associated with the term pit bull. When malevolent individuals turn to large (60+ kg) dog breeds that are not as inherently human-friendly, such as the Boerboel, Tosa Inu, Akita Inu, Fila Brasileiro, Dogue de Bordeaux or Neopolitan Mastiff, it is highly unlikely that the situation of human safety will be improved.
Seventh, the attention is moved from the dog owner and breeder to the dog itself. It is considered a fact by many dog experts that no dog breed is aggressive by itself, and every dog can develop into a safe, friendly animal when handled properly. It is the responsibility of the owner to train the dog well and in a responsible manner, and it is the responsibility of the dog breeder not to breed with animals that can not be trusted, they should always be excluded from the program. Unfortunately, financial motivation often overrules the ethical attitude.
An alternative that might prove far more effective than BSL, is to set high standards for breeders of so-called "dangerous dogs" to make sure that they breed healthy, animals that are both safe and friendly to human beings. This could be coupled to the setting of penalties for breeders that ignore these standards.
Also, one can impose experience requirements on potential owners, so inexperienced owners are not allowed to handle a potentially dangerous dog. Potential owners should increase their awareness and responsibility to an extensive degree.