Marsh v. Oregon Natural Resources Council, 490 U.S. 360 (1989)
Marsh v. Oregon Natural Resources Council is a foundational Supreme Court decision at the intersection of environmental and administrative law.
Under NEPA and the CEQ regulations, and reviewed pursuant to the APA, what is the proper standard for judicial review of an agency's decision not to prepare a supplemental EIS in light of new information, and was the Corps' decision here unlawful under that standard?
NEPA requires agencies to take a "hard look" at environmental consequences, but it does not mandate particular outcomes. CEQ regulations require supplementation of an EIS if there are significant new circumstances or information relevant to environmental concerns and bearing on the proposed action or its impacts, where major federal action remains to occur. 40 C.F.R. § 1502.9(c). Judicial review of an agency's decision not to supplement is governed by the APA, 5 U.S.C. § 706(2)(A), which asks whether the decision was arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law. Courts must be highly deferential to an agency's reasoned evaluation of technical and scientific data, ensuring only that the agency considered the relevant factors and articulated a rational connection between the facts found and the decision made. Review is generally confined to the administrative record, though courts may consider explanatory affidavits or testimony to illuminate the agency's reasoning without accepting post hoc rationalizations.
The Supreme Court held that an agency's decision not to prepare a supplemental EIS is reviewed under the APA's arbitrary-and-capricious standard, not a de novo or "reasonableness" standard. Applying that standard, the Court concluded the Corps' decision not to prepare a SEIS for the Elk Creek Dam—after taking a hard look at the new studies and expert opinions—was not arbitrary or capricious. The Court also held that it is permissible for a reviewing court to consider explanatory affidavits from agency officials to clarify technical issues and the agency's reasoning.
Marsh cements the APA's arbitrary-and-capricious standard as the lens through which courts review agency decisions concerning supplemental NEPA analysis. It teaches that NEPA's "hard look" is rigorous but deferential, especially on scientific and technical issues, and that courts must avoid second-guessing agencies where the record demonstrates reasoned evaluation. For litigants, Marsh underscores the centrality of the administrative record and the strategic importance of building, and then challenging, the agency's documented reasoning. For agencies, it confirms that thorough engagement with new information—documented in the record and supported by expert analysis—can sustain a decision not to prepare a SEIS.