36 C.F.R. § 17.7
On any property which has been in Federal ownership less than two years, the Secretary, in addition to the notice specified in § 17.4 , shall inform the last owner or owners of record by certified mail at their present or last known address of the highest bid on the interest and advise them of their right to acquire the interest for an amount equal to the highest bid if within 30 days they notify the Secretary of their desire to do so and make payment or agree to make payment of an amount equal to that specified in § 17.5 .
If within 30 days of mailing of such notification, the former owner or owners do not indicate a desire to acquire the interest and make payment or agree to make payment for such interest in an amount equal to the declared high bid, or, if they do indicate such a desire but fail to consummate the transaction within the time period established for the conveyance, then the bid of the declared high bidder will be accepted. In the event that a former owner who indicates a desire to repurchase pursuant to this procedure fails to consummate the transaction within the established time period the declared high bidder shall be permitted, but not required, to consummate the transaction. If the declared high bidder does not choose to consummate the transaction in this circumstance, the entire transaction will be cancelled, and, if appropriate, a new bidding procedure instituted.
36 C.F.R. §17.7