The ADA laws permit food service and grocery stores to ask only two questions when a person claims to be accompanied by a service dog.
1. Is this dog a service dog?
2. What is it trained to do?
If a person with a dog tells you the animals is a service dog, you must allow him into your restaurant or grocery store,
even if you suspect the person is not telling the truth.
Apparently there is a distinction between a service dog and a therapy dog, which is becoming more commonplace for former veterans with PTSD, and therapy dogs do not have the same privileges. See more at
Laws Regarding Dogs in a Grocery Store | Chron.com