I don't know if this is ableism but I found out that in the US service dogs don't have any kind of registration or paperwork that confirms they're a service dog.
I don't understand why not. My friend has a service dog and he can take out a document explaining what his dog is trained to do, who trained it, general legal information, and that confirms my friend needs a service dog and is allowed to bring it inside places where dogs would normally not be allowed in.
There are people who lie about their dogs being service dogs (I have met some myself, and lying about your dog being a service dog is ableism, in my opinion), and having a document makes it very easy to make sure no one lies about it.
I don't know if this is ableism from the ADA itself, because it would make it less likely for people with service dogs to be harassed about "not needing a dog" or being accused of lying. I still think this is as good as a place for me to ask, if that's okay. I don't have a service dog myself and my information comes from looking it up online and my friend telling me about it
I don't personally have a service dog, so I'm not sure about processes here and why there aren't papers, but I do see issues in the US where places will ask for papers which aren't necessary here resulting in more ableism.
I think an argument can be made that the lack of papers is accidentally ableist by inadvertently causing such situations.
Update - commentors point out how needing papers for service animal ownership is ableist.