My post wasn’t suggesting there’s “shades of gray” - the OP mentioned “a CAT” as if it’s ludicrous to even think they could perform legitimate service animal duties, so I showed that they do and can.I don't understand why there are people who think this has shades of grey. The language in the ADA is crystal clear. If I worked in an environment where people wanted to bring cats, iguanas and whatever else I would suggest that an enlarged copy of the text of the law about what animals can work in that environment be printed out, enlarges, laminated and securely attached to all of the doors. Include a web address for non-believers. Unqualified animals that enter and then perhaps cause problems make things difficult for those with legitimate service dogs by creating a skeptical environment.
The ADA is federal law which means it’s the minimum states must permit, but as someone replied above, individual states can have laws that allow for other animals. Think of it like marijuana: federally it’s not allowed but individual states have chosen to legalize medical marijuana or even marijuana without any need to prove a medical purpose.