30 U.S. Code § 209 - Suspension, waiver, or reduction of rents or royalties to promote development or operation; extension of lease on suspension of operations and production
The Secretary of the Interior, for the purpose of encouraging the greatest ultimate recovery of coal, oil, gas, oil shale  gilsonite (including all vein-type solid hydrocarbons),, phosphate, sodium, potassium and sulfur, and in the interest of conservation of natural resources, is authorized to waive, suspend, or reduce the rental, or minimum royalty, or reduce the royalty on an entire leasehold, or on any tract or portion thereof segregated for royalty purposes, whenever in his judgment it is necessary to do so in order to promote development, or whenever in his judgment the leases cannot be successfully operated under the terms provided therein.
 So in original. Probably should be followed by a comma.
 So in original.
 So in original. The period probably should be a colon.
1981—Pub. L. 97–78 inserted reference to gilsonite (including all vein-type solid hydrocarbons) and inserted proviso that, in order to promote development and the maximum production of tar sand, at the request of the lessee, the Secretary review, prior to commencement of commercial operations, the royalty rates established in each combined hydrocarbon lease issued in special tar sand areas, and that, for purposes of this section, “tar sand” means any consolidated or unconsolidated rock (other than coal, oil shale, or gilsonite) that either contains a hydrocarbonaceous material with a gas-free viscosity, at original reservoir temperature, greater than 10,000 centipoise, or contains a hydrocarbonaceous material and is produced by mining or quarrying.
1976—Pub. L. 94–377 inserted sentence at end that nothing in this section shall be construed as granting to the Secretary authority to waive, suspend, or reduce advance royalties.
1948—Act June 3, 1948, extended applicability of section to oil shale, phosphate, sodium, potassium, and sulphur.
1946—Act Aug. 8, 1946, principally inserted first and third sentences relating to waiver, suspension or reduction of royalties or rentals, and applicability of section to cooperative or unit plans, respectively.
See note set out under section 181 of this title.