According to the ADA service dogs do not need to be certified or wear anything identifying them as service dogs. There is no national organization that certifies service dogs, instead several independant organizations where you can ‘register’ your service dog and get paperwork saying your dog is registered. Legally, if someone has a service dog with them, the only questions they can be asked by the employees of the businesses they go to is “is the service animal required because of a disability?”.
My GSD is in training to be my PTSD service dog. When we go out places I put his “In Training” vest on because it does avoid some questions, and it keeps most people from trying to pet him. He still has an ‘In Training’ vest vs. a ‘Service Dog’ vest because he is not finished training yet, and from time to time he does not act like a finished service dog. He is still getting used to walking around stores with me when Im with someone else, he is sensetive to noise and if we are somewhere with a ver loud shrill noise he gets a little fidgity (Lowes making keys for example, he was in a sit/stay facing behind me to alert if anyone walked up and he kept quietly whining and trying to lay down.) Once I am 100% certian he will act as he should in every situation that arises, I will buy him the ‘Service Dog’ patches for his vest.
There are no rules or regulations about what breeds can or can’t be used as service dogs. As long as the dog is a good match with the handler, is capable of performing the tasks required by the handler, and is NOT aggressive, any dog can be used. Small dogs cannot be used for anyone that needs any mobility help, as the small dog wouldn’t be able to support any weight to help with mobility. Small dogs also cannot be used for autism dogs, as one of the big tasks for autism dogs is tethering, where the autistic child is wearing a harness and tethered to the dog (also wearing a harness). If the child tries to run off, the dog is trained to sit or lay down to resist the pressure and keep the child from running away.
My best friend trains service dogs, and she is helping me train my GSD in exchange for my help when she gets stuck on something with one of her dogs. So far I have seen her train boxers, pitbulls, laberdoodles, labs, pit/boxer mix, and GSDs as service dogs. There are several PTSD service dog organizations I follow on facebook that specifically choose to use rescued shelter dogs (with the right temperment) as service dogs. There are also organizations that have their own breeding programs and stick to specific breeds (labs, goldens, shepherds). Neither way is right or wrong, as long as they turn out well trained, well socialized dogs.