There is no certifications for service dogs, which makes this really tricky.
Anyone these days can claim to have a "service dog," trust me.
Have the lawyer check out--->http://animallaw.com
Nice database to search through, state by state!
Also he should chat with Kristen, moderator and owner of the site Service Dog Central. She can give you a great deal of info in regards to service dogs--->
http://www.servicedogcentral.org/content/ According to her, a service dog "...is trained to perform tasks that the disabled owner cannot do for themselves, and that mitigate that person's disability. It typically takes 18-24 months of expert training for a dog to become a service dog."
A service dog is "Effective February, 2011, “Service animal means any dog that is individually trained to do work or perform tasks for the benefit of an individual with a disability, including a physical, sensory, psychiatric, intellectual, or other mental disability. Other species of animals, whether wild or domestic, trained or untrained, are not service animals for the purposes of this definition. The work or tasks performed by a service animal must be directly related to the handler´s disability. Examples of work or tasks include, but are not limited to, assisting individuals who are blind or have low vision with navigation and other tasks, alerting individuals who are deaf or hard of hearing to the presence of people or sounds, providing non-violent protection or rescue work, pulling a wheelchair, assisting an individual during a seizure, alerting individuals to the presence of allergens, retrieving items such as medicine or the telephone, providing physical support and assistance with balance and stability to individuals with mobility disabilities, and helping persons with psychiatric and neurological disabilities by preventing or interrupting impulsive or destructive behaviors. The crime deterrent effects of an animal´s presence and the provision of emotional support, well-being, comfort, or companionship do not constitute work or tasks for the purposes of this definition.”
There are people who want to take their dogs everywhere and so to do that all they need is a letter from their doctor stating the dog is for such and such because we deem Mr/Mrs So and so disabled. There are scammer websites such as NSAR Service Dog Registry that is FAKE! All you have to do is pay X amount of dollars to "register" your dog and they will send you a badge, a vest and some certificate. Legit service do not have this! There is also another site where for another X amount of dollars you can have a set of doctors "determine" your need for a service/emotional service dog. All people have to do these days is pay money to have their non-trained pet dog as a "service animal."
Service dogs in the States do not, according to the site Service Dog Central, do not need to be certified.
When this goes to court, I personally think that the restaurant owners could win because they did ask the customer to control the dog and the customer ignored them. I can tell you that people who have legit service dogs would've 100% complied with the resteraunt owners.