Each state has their own laws regarding whether you can ask or not. In North Carolina the law is clearly stated in the general statutes. § 168-4.2. May be accompanied by service animal. (a) Every person with a disability has the right to be accompanied by a service animal trained to assist the person with his or her specific disability in any of the places listed in G.S. 168-3, and has the right to keep the service animal on any premises the person leases, rents, or uses. The person qualifies for these rights upon the showing of a tag, issued by the Department of Health and Human Services, under G.S. 168-4.3, stamped "NORTH CAROLINA SERVICE ANIMAL PERMANENT REGISTRATION" and stamped with a registration number, or upon a showing that the animal is being trained or has been trained as a service animal. The service animal may accompany a person in any of the places listed in G.S. 168-3.