Service dog regulation?

My friend recently had to bring his dog to stay at his apt. When the management found out about it they told him they were going to evict him, so naturally out of desperation he told them that it was a service dog, and purchased those tags off the Internet. The problem is now he is taking the dog everywhere with him, and impersonating someone disabled. The dog is extremly well behaved. I have tried to express the moral dilemma to him to no availe. I would like him to stop, but I know that the only thing that is going to persuade him is real tangible ENFORCEABLE penalties. I have tried to research this. I have read the ADA, but it doesn't seem like there is anyone who governs this. I have read that there are "huge fines and possible imprisonment" for this, but it seems that by law no one is allowed to ask you or make you prove that you actually have a disability. He is not stupid, so he has ligitimate answers for the three questions businesses are permitted to ask. I need to be able to give him an example of how he's going to get caught, or who is responsible for checking this, but I can't find one thing that answers this. Can anyone help me? Can the police ask you to prove that you have a disability? I read a story about a guy that had his own service dog and saw an imposter so he told the store and they called the police. But it seems they wouldn't be able to ask either. Does anyone know where i could find the actual law on this? Please help me I'm so frustrated. It's in Texas if that helps but I know federal law supersedes so?