28 CFR Part 35 Title II Notice of Proposed Rulemaking (NPRM) (published 2008)

(h) Prevention of fraudulent purchase of accessible seating.  A public entity may not require proof of disability before selling a wheelchair space.

(1) For the sale of single-event tickets, it is permissible to inquire whether the individual purchasing the wheelchair space uses a wheelchair.

(2) For season tickets, subscriptions, or other multi-events, it is permissible to ask the individual to attest in writing that the wheelchair space is for an individual who utilizes a wheelchair.  A public entity may investigate the potential misuse of accessible seating where there is good cause to believe that such seating has been purchased fraudulently.