No law states that dogs need to be registered to be a service or guide dog. Some people with disabilities, however, choose to register their dogs with service dog registries to avoid any possible public confrontation over the ability or skills of a service dog.
Under the Americans with Disabilities Act, any dog trained to perform identifiable tasks specific to a person's disability is considered a service dog regardless of whether the animal has been registered, licensed or certified by any independent organization or by the local or state government. Although registration is not mandatory, some states, such as California, encourage people with disability to get an identification tag for their service dogs to verify that the animal meets specific requirements. Once verified, both the dog and his owner are protected under the state law.
Even if a service dog does not have an identification tag, the ADA takes priority over the state or local laws and gives greater protection to persons with disabilities and their service animals. Any person covered by the ADA with a service dog may not need to provide any dog documentation, such as registration or proof of training or certification as a service dog, to any entity, business or establishment. The ADA is also not affiliated with any service dog registry.