43 CFR §3601.21

1. (a)Unless otherwise provided, if you are a purchaser under a sales contract or a free use permittee, you have the right to:
   1. (1)Extract, remove, process, and stockpile the material until the contract or permit terminates, regardless of any rights others acquire later under the provisions of the general land laws; and
   2. (2)Use and occupy the described lands to the extent necessary for fulfillment of the contract or permit.
2. (b)Users of the lands covered by your materials sales contract or free use permit who acquire their rights later than the date BLM designated the tract for mineral materials disposal will be subject to your existing use authorization, as provided in § 3602.12. This applies to uses due to any later settlement, location, lease, sale, or other appropriation under the general land laws, including the mineral leasing and mining laws.