This a very sticky subject. I am a service dog trainer as well as a new investor. The ADA is meant to protect a disabled person regarding privacy. So the animal does not have to be wearing any ID to signify that they are in fact a service animal. There is definitive distinction between a "support animal" which has not technically been certified as "service animal". On top of that, there is no governing entity monitoring who is even certifying these animals. It is not very understood by the public, but my husband and I have plans to change this issue. As far as your immediate needs, just because they say it is a service animal, its obedience shouldnt even ever have to be in question. If it is, they either failed to comply with re-newing their service cert "which is typically tested yearly or they were never certified by a real trainer in the first place. If they are a problem, you should speak with the ADA and a lawyer so you are protected from being sued for discrimination. Other than that, if they say it is a service animal, the only question you are leagally allowed to ask is "what task do they perform?" After that, you have to take their word for it.