It sounds like the other dog owners you come into contact with are a tad nosey/gossipy. I am a puppy raiser for the service dog organization, Canine Companions for Independence. http://www.cci.org By law, business can only ask two questions: "Is the dog a service animal required because of a disability?" and "What work or task has the dog been trained to perform?" Most medical alert dogs (seizure, diabetes, etc) are not trained the same as service dogs. Which means the dog may not have as extensive training/socialization as a service dog. I appreciate the fact that you are aware of the service dog fraud epidemic that is going on in this country. But, there is no governing body over service dogs and the general public shouldn't try to police the situation as it could just escalate the matter and make it worse.

I would suggest asking the two questions I listed above and pay close attention to their answers. A service dog handler is not required by law to reveal their disability but sometimes when answering the first question that information is volunteered. So, that may tell you that the dog is a medical alert dog and therefore may not be the same type of working dog as you are used to seeing. Based on how your client answers the second question it maybe revealed that the dog was in fact professionally trained. If so, you may ask if XYZ organization offers refresher training classes for the dog. Self trained service dogs are covered under ADA law but usually have less socialization then a service dog that is professional trained. If your client asks why you are asking these questions just let s/he know that other dog owners were asking because of some of the behaviors "fluffy" is exhibiting. Reassure your owner that you were only inquiring so that you can let them know that "Fluffy" is starting to exhibit some negative behaviors and it could possibly become a safety issue or hinder their public access in the future.

If you do not feel better about the situation once you have this discussion I would let the owner know that until "fluffy" has a refresher course in training (either professionally or private/personal) you will not be able to continue provide dog walking services as you have safety and liability concerns.

Hope this helps! Beth