28 CFR Part 35 Nondiscrimination on the Basis of Disability in State and Local Government Services (2010 ADA Title II Regulations with amendments issued through Aug. 2016)

(f) Inquiries. A public entity shall not ask about the nature or extent of a person's disability, but may make two inquiries to determine whether an animal qualifies as a service animal. A public entity may ask if the animal is required because of a disability and what work or task the animal has been trained to perform. A public entity shall not require documentation, such as proof that the animal has been certified, trained, or licensed as a service animal. Generally, a public entity may not make these inquiries about a service animal when it is readily apparent that an animal is trained to do work or perform tasks for an individual with a disability (e.g., the dog is observed guiding an individual who is blind or has low vision, pulling a person's wheelchair, or providing assistance with stability or balance to an individual with an observable mobility disability).