For people who they help, it's not so bad. A cat in an apartment, for example, can be pretty unobtrusive, and can be in the realm of reasonable accommodations (pun not intended). A parrot is a different story, and a dorm room is a different story. For ESAs, and accommodations in general, if it isn't judged to be in the realm of reasonable, like if someone had an untrained great dane that they wanted to bring into a dorm room (clearly unreasonable), then I'm 99% sure that can be denied. Like if someone medically can't lift 30 lbs, then there isn't really anything reasonable you can do to accommodate that on a construction yard. Even service animals, if they're disruptive (like barking at customers or pooping on the floor of a restaurant), can get kicked out.