14 CFR § 250.6 - Exceptions to eligibility for denied boarding compensation.
A passenger denied boarding involuntarily from an oversold flight shall not be eligible for denied boarding compensation if:
(a) The passenger does not comply fully with the carrier's contract of carriage or tariff provisions regarding ticketing, reconfirmation, check-in, and acceptability for transportation;
(b) The flight for which the passenger holds confirmed reserved space is unable to accommodate that passenger because of substitution of equipment of lesser capacity when required by operational or safety reasons; or, on an aircraft with a designed passenger capacity of 60 or fewer seats, the flight for which the passenger holds confirmed reserved space is unable to accommodate that passenger due to weight/balance restrictions when required by operational or safety reasons;
(c) The passenger is offered accommodations or is seated in a section of the aircraft other than that specified on the ticket at no extra charge, except that a passenger seated in a section for which a lower fare is charged shall be entitled to an appropriate refund; or
(d) The carrier arranges comparable air transportation, or other transportation used by the passenger at no extra cost to the passenger, that at the time such arrangements are made is planned to arrive at the airport of the passenger's next stopover or, if none, at the airport of the final destination not later than 1 hour after the planned arrival time of the passenger's original flight or flights.