The animal rights organization PETA initiated a lawsuit on Tuesday aiming to compel the American Kennel Club to drop the breed standards it endorses for popular breeds like French bulldogs. PETA claims the club is endorsing physical traits that compromise the animals’ health.

The lawsuit brings attention to a significant point of contention in the dog world: the specific characteristics that have been emphasized in certain breeds. Notably, the French bulldog, which holds the title as the most popular breed in the U.S. according to the AKC.

PETA argues in the lawsuit that the AKC’s official breed guidelines for dogs such as the bulldog, French bulldog, pug, dachshund, and Chinese shar-pei suggest frameworks that encourage breeding dogs with deformities and poor health.

The AKC said it’s committed to protecting “the health, heritage and well-being of purebred dogs” and that responsibly bred dogs that conform to the standards are healthy.

“We categorically reject PETA’s mischaracterizations of specific breed standards and their assertion that these standards create unhealthy dogs,” the club said in a statement, adding that dog health and welfare is “paramount and at the core of our mission.”

Founded in 1884, the New York-based AKC is a nonprofit that acts like a league for many canine competitions and runs the United States’ oldest dog registry, where owners may choose to document their dogs’ existence and accomplishments. Mixed-breed dogs and rescues can be registered as “canine partners” and compete in some sports, but the club’s history is closely tied to fanciers who cultivate and show purebreds.

Each breed has its own club that sets the “standard,” or ideal characteristics, for the dogs. The AKC reviews, approves and promulgates them.

PETA, also called People for the Ethical Treatment of Animals, describes itself as an animal liberation organization. Its advocacy includes boycotts and litigation. Its supporters are known for staging sometimes disruptive protests in settings including a papal audience, a Starbucks and sporting events such as the Westminster Kennel Club dog show.

The Norfolk, Virginia-based nonprofit opposes dog breeding in general and has clashed for years with the AKC.

Peppered with photos and diagrams, PETA’s new lawsuit runs through health problems that can beset short-legged, long-backed dachshunds (“the animal equivalent of a poorly designed bridge,” in PETA’s view) and shar-peis, which can have spates of fever and inflammation known as “shar-pei autoinflammatory disease.” The complaint points to pugs’ risk of injuries to their marbly eyes and susceptibility to breathing problems and overheating because of their flat faces.

The suit zeros in on those and other parts of bulldogs and Frenchies, including the big heads that often prompt caesarian births.

The various problems that PETA cites don’t afflict all dogs of these breeds, and some do agility, dock diving and other sports. But the conditions can be serious for those that have them.

In the U.K. – where research involving about 24,600 dogs suggested that Frenchies have “very different, and largely much poorer” health than do other canines – the British Veterinary Association campaigns against advertisements that feature flat-faced breeds. The Netherlands has prohibited breeding very short-snouted dogs.

Norway’s Supreme Court, however, declined to block the breeding of English bulldogs – but upheld a lower court’s prohibition on breeding cavalier King Charles spaniels, citing a different set of health concerns.

The AKC says the breed standards it approves reflect “decades of collaboration with veterinary experts and breeders.” Some breed clubs donate to and participate in dog health research, and the AKC says it has given over $40 million since 1995 to its canine health research charity.