And to all the "I'll just get a Dr.'s Note" people......While ADA doesn't allow the rangers to ask what your disability is.....they can ask for proof of disability by way of a State issues placard, similar to Handicap Parking placards.....Dr.'s are not going to hand these out and risk losing their licenses for falsifying ADA laws.
"(c)(1) Inquiry about disability. A public entity shall not ask an individual using a wheelchair or other power-driven mobility device questions about the nature and extent of the individual´s disability.
(2) Inquiry into use of other power-driven mobility device. A public entity may ask a person using an other power-driven mobility device to provide a credible assurance that the mobility device is required because of the person´s disability. A public entity that permits the use of an other power-driven mobility device by an individual with a mobility disability shall accept the presentation of a valid, State-issued, disability parking placard or card, or other State-issued proof of disability, as a credible assurance that the use of the other power-driven mobility device is for the individual’s mobility disability. In lieu of a valid, State-issued disability parking placard or card, or State-issued proof of disability, a public entity shall accept as a credible assurance a verbal representation, not contradicted by observable fact, that the other power-driven mobility device is being used for a mobility disability. A "valid" disability placard or card is one that is presented by the individual to whom it was issued and is otherwise in compliance with the State of issuance´s requirements for disability placards or cards."