In a significant decision interpreting the National Environmental Policy Act (NEPA), the U.S. Supreme Court issued its opinion in Seven County Infrastructure Coalition v. Eagle County, Colorado on May 29, 2025. For certain projects, NEPA requires federal agencies to prepare Environmental Impact Statements (EIS) that detail significant environmental effects of the proposed action along with reasonable and feasible alternatives. The holding in Seven County clarifies the appropriate scope of environmental review under NEPA and reaffirms the deference owed to federal agencies in preparing an EIS.

The case arose from a proposal to construct an 88-mile railway connecting Utah’s oil-rich Uinta Basin to the national railway system. The proposed railway would be used primarily to transport crude oil to refineries along the Gulf Coast. As required by NEPA, the U.S. Surface Transportation Board (STB), the agency responsible for authorizing new railroad construction, prepared a 3,600-page EIS analyzing the environmental impacts of the railway’s construction and operation. The EIS analyzed the environmental effects of the railway but did not fully analyze the potential environmental effects of increased upstream oil drilling in the Uinta Basin or downstream refining activities in the Gulf. After a public review period, the STB issued a final EIS and approved the project. A local Colorado county and several environmental organizations challenged the STB’s approval in the D.C. Circuit Court of Appeals. The D.C. Circuit vacated the approval, holding that the EIS violated NEPA by failing to adequately consider the reasonably foreseeable environmental impacts of upstream and downstream oil-related activities.

The Supreme Court unanimously reversed the D.C. Circuit. In a majority opinion by Justice Kavanaugh, the Court held that the D.C. Circuit failed to afford the STB the “substantial deference” required under NEPA and misinterpreted the statute’s requirements. First, the Court ruled that the “central principle of judicial review in NEPA cases is deference.” It emphasized that NEPA is a “purely procedural statute” designed to “inform agency decisionmaking, not to paralyze it.” Unlike agency interpretation of a statute—which courts review as a matter of law, see Loper Bright Enters. v. Raimondo, 603 U.S. 369 (2024)—when preparing an EIS, the agency is acting under the discretion granted by NEPA, and the agency’s decision should be given deference when the agency action was “reasonable and reasonably explained.” The Court recognized that agency preparation of an EIS requires “a series of fact-dependent, context-specific, and policy-laden choices about the depth and breadth of its inquiry—and also about the length, content, and level of detail of the resulting EIS.” The Court reasoned that reviewing courts must be at their “most deferential” when reviewing such fact-based determinations regarding scope and content of an EIS, and therefore “the question of whether a particular report is detailed enough . . . should not be excessively second-guessed by a court.”

Second, the Court ruled that NEPA does not obligate agencies to analyze environmental effects of upstream or downstream activities that are “separate in time or place” from the “project at hand” and “fall outside the agency’s regulatory authority.” The Court distinguished between indirect environmental effects—like “run-off into a river that flows many miles from the project and affects fish populations elsewhere”—that are within the scope of a single project, and environmental effects from “future or geographically separate projects”—like upstream oil production and downstream refining activities—that constitute separate independent projects. In explaining what constitutes a separate project, the Court explained that “the textually mandated focus of NEPA is the ‘proposed action.’” In addition to the statutory text, the Court held that a “but for” relationship alone does not require an agency to explore a particular effect in an EIS . Instead, relevant environmental effects must be “interrelated and close in time and place to the project at hand.”  Acknowledging that “[t]here may be a gray area in defining the project at hand,” the Court reaffirmed that courts should give agencies “substantial deference” regarding the scope of their own NEPA review, which must remain within the bounds of their inherent regulatory authority. For example, the STB is authorized to regulate railway projects, but not oil drilling or oil refineries. Therefore, the STB could evaluate effects from the railway’s construction and operation, which it was authorized to regulate, but it had no obligation to consider the effects of separate upstream and downstream projects.

The Court’s holding makes clear that “NEPA is a procedural cross-check, not a substantive roadblock,” and that a “course correction” is necessary “to bring judicial review under NEPA back in line with the statutory text and common sense.” Under Seven County agencies are given significant deference to draw a “manageable line” as to where the effects of a proposed action begin and end. Likewise, courts should not “micromanage [these] agency choices so long as they fall within a broad zone of reasonableness.” And when faced with “gray areas”, where a court thinks the agency should have drawn a different line, the court should defer as long as line the agency drew was “reasonable and manageable.”