The trending practice of disguising one’s dog as a service animal to gain conveniences — such as preferential seating or service afforded to the disabled — is surprisingly common, according to advocates for people with disabilities.

So pervasive are these fake “guide dogs” that Canines for Independence, the nation’s largest organization of service dog breeders and trainers, has asked the U.S. Justice Department to prohibit the online sale of materials used to fake the act, such as documentation and identifying patches placed on the dog.

Thousands of people have purchased such materials to use dogs for preferential treatment while shopping, traveling, and even nightclubbing. “People think what they’re doing is harmless but it’s not — it’s very harmful,” Marcie Davis, a paraplegic who uses a service dog, told CBS News. “This is jeopardizing people like me who really need a service dog. It’s jeopardizing our ability to be a working team out in public.”

Davis, who founded International Assistance Dog Awareness Week, says the canine fakery undermines advocacy work seeking public acceptance and accommodation of people with disabilities, a generation after the Americans with Disabilities Act first outlawed discrimination against disabilities in employment, transportation, public accommodation, communications, and government activities.

The New York Post this summer wrote of several dog owners who have faked the routine, taking their act to malls, movie theaters, and nightclubs. “He’s been to most movie theaters in the city and more nightclubs than most of my friends,” a 33-year-old New York City resident said of his Yorkshire terrier.

Another dog owner also described the unscrupulous scheme in an online video. “I took Bubs out for a walk and it started raining and I don’t feel like walking him home so we’re going to get on the bus and I’m going to make him a disabled dog,” he said. “This service dog scam works pretty good.”

Federal law requires people with service animals to possess basic documentation certifying the animal, but forbids anyone from asking about the nature of the disability. Thus, fakers may simply pass themselves off as emotionally fragile creatures requiring a “companion animal,” without faking blindness or severe physical disability.

Davis and other advocates for the disabled describe the ease of purchasing such fakery materials online. “If you provide a photo, then you can get an ID,” Davis said. Indeed, an online search by Google on Wednesday for “service dog vest” yielded 1.8 million hits, with a plethora of options for terrier-sized dogs in the $32 range.

Dog owners employing a service canine without proper documentation do the disabled a disservice, Davis said. “My second assistance dog was actually attacked by a dog at a professional conference by someone who was trying to pass off their pet as assistance dog [but] had no business being in public,” she said. “They’re disruptive, they’re eating food in restaurants and they’re acting very inappropriately,” Davis added, contrasting the behavioral profile to the trained dog, quiet and calm in public. “They’re supposed to very quiet and go under a table or chair and really be unseen when they are out in public.”

Although several states may update disability law to prohibit the fakery, New Mexico is the only state that currently outlaws the con.