Actually, they don't need to be licensed. The only thing a business can ask is what tasks is the service dog trained to be formed.
I do think it would be better off for everyone if there was a license though. I've known people with legitimate service dogs who have had that opinion even. They wish they had a document to prove their legitimacy, as they are constantly asked for a document that doesn't exist.
That requirement always felt weird. I can’t ask what disability a person has, but I can ask what the dog is supposed to do? Because if they say it helps alert to a seizure, I just learned they possibly have chronic seizures without actually asking that.
Oh, thanks for correcting me, I thought there was a license involved in the US, or at least some kind of certification that the animal actually is trained, and that you didn't just slap a vest on your pet poodle...