43 CFR § 3432.3 - Terms and conditions.
(a) The terms and conditions of the original lease shall be made consistent with the laws, regulations, and lease terms applicable at the time of modification except that if the original lease was issued prior to August 4, 1976, the minimum royalty provisions of section 6 of the Federal Coal Leasing Amendments Act of 1976 (30 U.S.C. 207; 43 CFR 3473.3–2) shall not apply to any lands covered by the lease prior to its modification until the lease is readjusted.
(b) Before a lease is modified, the lessee shall file a written acceptance of the conditions imposed in the modified lease and a written consent of the surety under the bond covering the original lease to the modification of the lease and to extension of the bond to cover the additional land.
(c) Before modifying a lease, BLM will prepare an environmental assessment or environmental impact statement covering the proposed lease area in accordance with 40 CFR parts 1500 through 1508.
(d) For coal lease modification applications involving lands in the National Forest System, BLM will submit the lease modification application to the Secretary of Agriculture for consent, for completion or consideration of an environmental assessment, for the attachment of appropriate lease stipulations, and for making any other findings prerequisite to lease issuance.