The Federal Land Policy and Management Act (FLPMA), 43 U.S.C. § 1732(b), required the Bureau of Land Management (BLM) (defendant) to take any action necessary to prevent the unnecessary or undue degradation (UUD) of public lands. In 1980, the BLM issued regulations that used a prudent-operator standard to interpret the UUD requirement. In 2000, the regulations were amended to include a more stringent standard of substantial irreparable harm (SIH). The SIH standard allowed the BLM to deny mining plans of operations that would cause substantial irreparable harm to significant scientific, cultural, or environmental resources. Following a change in administration, the BLM wrote an opinion finding that the SIH standard could not be sustained because the terms “unnecessary” and “undue” were not distinct. In 2001, the regulations were amended to eliminate the SIH standard on the basis that implementation would be difficult, expensive, and potentially subjective. The Mineral Policy Center and other non-profit organizations (plaintiffs) challenged the 2001 regulations in federal district court, claiming that the regulations were inconsistent with FLPMA because they ignored the “undue” language and only prevented mining disturbances that were greater than necessary. The BLM claimed that it would protect public lands from UUD on a case-by-case basis by (1) approving or rejecting mining plans of operations, (2) regulating exploration activities that did not require plans of operations, (3) requiring financial guarantees for mining-activity costs, and (4) linking performance standards to existing laws and regulations. Both parties moved for summary judgment.