Jim: there are two laws covering Title II (government) and Title III (private/commercial) entities. In both cases, NO ONE may ask if an animal (dog or miniature horse) is certified, trained or licensed. Nope - can't even ask the question, by law!
Neither law requires certification or licensing. At most, the laws are very broad and only says "trained" to perfom a task or tasks.
The links below will take you close to the parts coverring "Inquiries." There are only two question one may ask: [an entity] "may ask if the animal is required because of a disability and what work or task the animal has been trained to perform."
You are NEVER allowed to ask the individual ABOUT the persons disability, ever! It's private information covered by not only the two laws below, but HIPPA as well.
Here are links to both laws, and as close to the "Inquiries" sections as I can get you:
1) Title II Entities (e.g. Governments):
2) Title III Entities (e.g. hotels, stores, etc):
GOOD LUCK and THANK YOU for your service to our Country and communities! Please pet Snickers once for me, and thank him for his service, too!