43 C.F.R. § 3435.1
Where the Secretary determines that coal exploration, development and mining operations would not be in the public interest on an existing lease or preference right lease application or portions thereof, or where the Congress has authorized lease exchange for a class or list of leases, an existing lease or preference right lease application may be relinquished in exchange for:
[44 FR 42628, July 19, 1979, as amended at 47 FR 33144, July 30, 1982]