Well maybe housing laws wasn't the right way to say it. I meant landlord pet rules.
http://servicedogcentral.org/content/faq/63
http://answers.yahoo.com/question/index?qid=20080331190914AA8xB4j
"You asked whether or not you can request paperwork to identify a Service Dog, and the answer is NO.
You cannot request paperwork, identifying clothing or vests, ID tags (even though in some counties in California one is required, Federal law supercedes all state and local agency laws and therefore not everyone who has a SD resides in that county, which requires the tag, and so it is not legally required and the person with the SD would win in court).
So, no ID tag, no paperwork, no vest, no cards...there is absolutely nothing required of a service dog user according to the ADA of 1990.
Furthermore, you may violate a person's rights by asking them for such things and the patron was exactly correct in telling you that her rights were being violated by your request.
You may only ask a service dog user 3 questions.
The legal questions you may ask are:
1) Are you disabled?
2) Is this a service animal?
3) What tasks does this animal provide you with?"
That is why it is so easy to get away with it having a fake service/emotional support animal. If you suspect the person is lying and call them on it and are wrong you are an EVIL SOB and will end up on the news labeled as the scum of the Earth at best or at worst sued. So most people just get away with it.