28 CFR Part 36 Nondiscrimination on the Basis of Disability by Public Accommodations and in Commercial Facilities NPRM (2008 Title III NPRM)

(6) Inquiries. A public accommodation shall not ask about the nature or extent of a person's disability, but can determine whether an animal qualifies as a service animal. For example, a public accommodation 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 accommodation shall not require documentation, such as proof that the animal has been certified or licensed as a service animal.