As I understand it, there is essentially
no bar to qualify for "service animal."
Famously, the ADA states that the only thing the staff of a public accommodation or establishment may do, is ask only two questions of a person purporting to have a service animal: (1) is the dog a service animal required because of a disability, and (2) what work or task has the dog been trained to perform. The thing is,
the ADA contains no requirement that the person provide a truthful answer to those questions. And thus the system seems ripe for abuse, and it's actually really surprising we haven't seen more of it.
With the ADA in place, you can take fluffy into a Michelin five-star restaurant. If the maître d' says "I'm sorry, sir, we don't allow pets," you can simply lie and say "this is a service animal which I require because of a disability." And at that point they're hamstrung. All they can do is ask you "what work or task has the dog been trained to perform?" And you can simply lie again and say "he nudges me with his nose to alert me if I'm about to have a seizure." They're not allowed to ask for any evidence whatsoever that you have a seizure disorder, or that the dog has in fact been trained to perform this task. If they do, they're violating the ADA. Your word as an allegedly "disabled" person is sacrosanct. Sure, if they
really feel certain you're lying, they can try to call your bluff and kick Fluffy out anyway, because if it went to court, there would subpoenaing of medical records and expert witnesses and such, and
then you'd have to actually provide evidence for your assertions. (Not to mention that you could also face penalties if you live in
one of many states which make it illegal to misrepresent a non-service animal as a service animal.) But do you really think they're going to risk bringing down a federal agency on them?
I'm honestly shocked more cluster B people aren't doing this. Why ask a doctor for an "emotional support animal" letter, when you can just lie and say your pet is a service animal?