On May 29, 2025, in a decision long-awaited by project developers, the Supreme Court issued Seven County Infrastructure Coalition v. Eagle County, Colorado, which clarified the proper scope of review and deference to be afforded to agency decisionmaking under the National Environmental Policy Act (NEPA). This decision reinforces longstanding Supreme Court holdings and may help improve the NEPA process by providing support for agencies to focus their NEPA reviews on impacts associated with their authorizations.

Background 

In Seven County, the U.S. Surface Transportation Board (Board) prepared a 3,600 page environmental impact statement (EIS) to evaluate a proposal by seven Utah counties to construct an 88-mile railroad line connecting Utah’s oil-rich Uinta Basin to the national rail network. The EIS acknowledged the potential upstream environmental effects from additional oil drilling projects in the Uinta Basin and potential downstream environmental effects of increased oil refining along the Gulf Coast, but found that those impacts did not need to be analyzed in further detail. The D.C. Circuit vacated the EIS and the Board’s final approval of the railway, finding that the Board erred by failing to analyze those potential upstream and downstream effects in the EIS.

The Supreme Court’s Decision

In a unanimous decision authored by Justice Kavanaugh, the Court reversed the D.C. Circuit and held that (1) NEPA requires courts to afford agencies “substantial judicial deference,” and (2) NEPA does not require the Board to evaluate “effects from potential future projects or from geographically separate projects.” The Court also found it salient that the Board would have no authority over such projects. Notably, all eight Justices who took part in the decision concurred in the judgment on the basis that it was consistent with the Court’s longstanding NEPA precedent.

The Court began its analysis by reinforcing the fundamental principle that NEPA is a purely procedural statute; it does not mandate particular results, but simply prescribes the necessary process for an agency’s environmental review of a project. It proceeded to explain that the D.C. Circuit erred both on the deference afforded to the Board’s decisionmaking and on its review of the merits.

Deference

The Court stated that “when determining whether an agency’s EIS complied with NEPA, a court should afford substantial deference to the agency.” In the context of NEPA reviews, agencies are forced to make numerous determinations of fact and policy; the Court “doubly underscored” that NEPA is inherently a “rule of reason,” and lower courts may not substitute their judgement for that of the agency as to the environmental consequences of its actions. The Court noted that agencies are in the best position to “determine whether and to what extent to prepare an EIS.” When it comes to environmental effects associated with a proposed project, feasible alternatives to that project, and the scope of effects to be analyzed (i.e., indirect effects or effects from future or geographically separate projects), it is the agency’s role to draw an appropriate line, “so long as [those decisions] fall within a broad zone of reasonableness.”

The Court observed that some reviewing courts have not applied NEPA correctly and, instead, have “engaged in overly intrusive (and unpredictable) review.” The Court concluded that, absent a “course correction of sorts,” this application of NEPA will continue to hamstring new infrastructure and construction projects. When evaluating an EIS for deficiencies, reviewing courts must keep in mind that NEPA is “purely procedural,” only obligating an agency to prepare an adequate report, and does not impose any substantive constraints on the agency’s ultimate decision to approve or support a project. In short, “[t]he bedrock principle of judicial review in NEPA cases can be stated in a word: Deference.”

The Court also found that even if an EIS is deficient in some aspects, those deficiencies do not necessarily require a reviewing court to invalidate an agency’s decision to approve a project. 

Merits

On the merits, the Court concluded that NEPA does not require an agency to evaluate environmental effects from separate projects that may occur in the future or are geographically distinct, reiterating its holding in Department of Transportation v. Public Citizen that the effects of a separate project need not be considered under NEPA because the separate project breaks the chain of proximate causation. Here, the Uinta Basin Railway was the relevant project and the Court concluded that nothing in NEPA required the Board to study environmental impacts from separate upstream or downstream projects. In other words, a mere “but for” causal relationship is insufficient to make an agency responsible for a particular effect.

The Court recognized that indirect effects—i.e., environmental effects generated by the project that occur later in time or outside the project’s location—may fall within NEPA, but consideration of such effects is different than an agency considering effects of separate projects that may result. The Court concluded that NEPA does not require the latter.

Key Takeaways

Seven County is significant for numerous reasons, including:

• It reinforces the longstanding principle that NEPA is a purely procedural statute, and it instructs courts to account for that principle when considering the reasonableness of the agency’s decisionmaking.
• It highlights the significant deference that is to be afforded to agency decisionmaking under NEPA.
• It preserves and reinforces the “proximate cause” standard articulated in Public Citizen for assessing the connection between the federal agency action and the environmental effects of a separate activity. It also confirms that “but-for” causation is not sufficient to demonstrate that an effect should be analyzed.
• The decision is also noteworthy for its commentary on how NEPA litigation has negatively impacted project development. The Court noted that project opponents may not always be motivated by their concern for the environment, instead using NEPA to prevent new infrastructure projects. The end result is that “fewer projects make it to the finish line. Indeed, fewer projects make it to the starting line. Those that survive often end up costing much more than is anticipated or necessary, both for the agency preparing the EIS and for the builder of the project.” To the extent the Court’s decision helps clarify and improve the NEPA review process and makes it more difficult to set aside an agency’s NEPA review, this decision may spur additional development and innovation.
• The Court’s finding that a determination that a NEPA review is inadequate in some respects does not necessarily require a reviewing court to invalidate an agency’s approval may result in more lower court decisions declining to vacate or set aside NEPA reviews, even where there may be some deficiencies.

Daniel C. Warren and Thurston Moore also contributed to this article. 

*Thurston Moore is a Summer Associate at Hunton Andrews Kurth LLP and is not admitted to practice law.