NEPA environmental review applies to most federal science and energy projects, and the amount of review depends on how much the project could affect the environment. The agency first asks whether a categorical exclusion covers the action. If not, it writes a short environmental assessment, and only projects with a reasonably foreseeable significant effect need a full environmental impact statement. NEPA review is a bigger deal than it sounds because it sits in front of the permit, the grant or the land use decision. This guide covers US federal law as of October 1, 2026, a period of fast change.

Three things have shifted in the last three years: Congress rewrote parts of the statute, the Supreme Court told judges to defer to agencies, and the White House office that wrote the old rules withdrew them.

What NEPA requires, in plain terms

NEPA is a procedural law. It does not tell an agency to pick the greenest option. It tells the agency to look before it leaps and to show its work. For major federal actions that significantly affect the human environment, the statute, codified in 42 U.S.C. 4332, calls for a detailed statement covering:

  • the reasonably foreseeable environmental effects of the proposal;
  • the reasonably foreseeable adverse effects that cannot be avoided;
  • a reasonable range of feasible alternatives, including doing nothing;
  • the relationship between short-term uses and long-term productivity;
  • irreversible and irretrievable commitments of federal resources.

Other rules still apply on top. The Endangered Species Act, the National Historic Preservation Act and state and local laws sit outside NEPA, as an Orrick analysis pointed out.

Does your project count as a federal action?

Only a “major Federal action” triggers the law. The definition, in 42 U.S.C. 4336e, covers an action the agency decides is subject to “substantial Federal control and responsibility.” The text then lists what does not count, including:

  • non-federal actions with no or minimal federal funding or involvement;
  • general revenue sharing funds;
  • loans, loan guarantees and other financial help where the agency lacks sufficient control over how it is used;
  • enforcement actions;
  • activities with effects entirely outside US jurisdiction;
  • non-discretionary decisions made under the agency’s statutory authority.

In practice, a privately funded laboratory on private land with no federal permit is outside NEPA. A new energy line that crosses federal land and needs a right-of-way usually is not.

The three tiers of review

Under 42 U.S.C. 4336, the agency works through a sequence. An agency need not prepare an environmental document at all when the action is not a final agency action, when a categorical exclusion applies, when preparing the document would clearly conflict with another law, or when the action is non-discretionary and the agency cannot consider environmental factors in deciding. If none of those apply, the project lands in one of two tiers.

Tier When it applies Statutory page limit Statutory deadline
Categorical exclusion The action fits a category the agency has found does not normally cause significant effects None None
Environmental assessment (EA) No significant effect is reasonably foreseeable, or significance is unknown 75 pages 1 year
Environmental impact statement (EIS) A reasonably foreseeable significant effect on the human environment 150 pages, or 300 for extraordinary complexity 2 years

The page limits and deadlines come from 42 U.S.C. 4336a. The page limits exclude citations and appendices. The clocks run from the earliest of certain triggers, such as a decision that an EIS is needed or a notice of intent. If an agency cannot meet its deadline it may extend it, but only by the extra time needed. A project sponsor can petition a court over a missed deadline, and the court’s schedule generally cannot exceed 90 days.

A project sponsor may also prepare the EA or EIS itself under agency supervision, though the agency must evaluate the document independently and take responsibility for it.

Timeline: how the rules shifted

  1. June 3, 2023: the Fiscal Responsibility Act adds the deadlines, page limits and other changes to the statute.
  2. May 1, 2024: the Council on Environmental Quality (CEQ) issues rules implementing those amendments, according to the Harvard Environmental and Energy Law Program’s tracker.
  3. February 2025: CEQ issues an interim final rule rescinding its NEPA regulations. Sources give February 2 and February 25 for this step, so the exact date is unsettled.
  4. May 29, 2025: the Supreme Court decides Seven County Infrastructure Coalition v. Eagle County.
  5. July 2025: several agencies, including Interior, Energy and Agriculture, issue new NEPA procedures.
  6. September 29, 2025: CEQ issues NEPA guidance relying on Seven County.
  7. January 2026: CEQ publishes a final rule eliminating its NEPA regulations. Orrick dates it to January 6, while Harvard’s tracker says January 8.
  8. April 9, 2026: new CEQ guidance on categorical exclusions replaces its 2010 guidance.
  9. June 29, 2026: CEQ withdraws 18 guidance memos issued between 1976 and 2024.

What Seven County changed for courts

This case is the biggest shift on the judicial side. Justice Kavanaugh’s majority opinion, joined by four colleagues, called NEPA “a procedural cross-check, not a substantive roadblock.” Read the opinion on Cornell’s site.

The Court held that judges should give agencies “substantial judicial deference” and not micromanage choices within a broad zone of reasonableness. It also held that the agency did not have to study the effects of separate upstream oil drilling or downstream refining. Effects of the project itself, including indirect ones, remain in scope. And even a deficient EIS does not automatically require vacating the approval. Three justices concurred in the result on narrower grounds, and Justice Gorsuch took no part.

For anyone planning a science facility or energy project, that means challengers face a higher bar, though NEPA documents still need to cover the project’s own effects and real alternatives.

No CEQ rulebook: what governs now

CEQ’s regulations, which for decades set common definitions across government, no longer exist. According to Orrick’s January 2026 analysis, each agency’s own rules, guidance and policies now set the framework, informed by CEQ’s September 2025 guidance. Agencies are to revise their procedures, and Orrick says the timeline for that work is unclear.

The practical consequence is that two federal agencies may handle similar projects differently. Before starting, check the specific agency’s current NEPA procedures. The statutory limits in the table above still apply, because they are in the law and not in CEQ’s rules.

Categorical exclusions are getting wider use

The April 2026 guidance, as summarized by the Harvard tracker, lets agencies adopt existing exclusions from other agencies, allows multiple agencies to rely on one lead agency’s determination, and drops the prior requirement for public notice and comment before issuing or revising exclusions. The statute itself sets a procedure for adopting another agency’s exclusion, in 42 U.S.C. 4336c: identify the exclusion, consult the agency that created it, tell the public, and document the adoption. Whether the guidance and the statute line up on consultation is a point I did not resolve.

Why science projects get caught

People tend to picture NEPA as a pipeline or highway law. It reaches further. A federally funded research station, a telescope site on federal land, a test range or a grid connection that needs a federal permit can all be federal actions. Whether any of them gets a quick exclusion or a multi-year statement depends on location and scale, not on the label “science.” A small instrument deployment on previously disturbed ground may fit an exclusion, while a large facility near a wetland will likely need at least an assessment. That is a general illustration rather than a rule from the statute, so a sponsor should ask the lead agency early.

A practical checklist for a sponsor

  1. Confirm there is a federal hook: a permit, a grant with real federal control, federal land or a license.
  2. Find the lead agency and read its current NEPA procedures.
  3. Ask whether a categorical exclusion fits.
  4. If not, plan for an EA or EIS, with its statutory page limit and clock.
  5. Decide whether the sponsor will prepare the document under agency supervision.
  6. Build in other reviews, such as species and historic-property consultations.

Common questions

Does NEPA apply to private projects?

Only if there is substantial federal control or responsibility, such as a federal permit or funding with real oversight. Purely private actions with minimal federal involvement are excluded by the statute.

Can a court still stop a project over NEPA?

Yes, but it is harder. Seven County says a deficient EIS does not automatically mean the approval is vacated, and courts must defer to reasonable agency decisions.

Is the old CEQ 2020 or 2024 rule still in force?

No. CEQ rescinded its regulations entirely, and sources describe a final rule in January 2026.

How long does review take?

The statute sets two years for an EIS and one year for an EA, from the triggering event. Real timelines vary by agency and project.

This article is general information about US federal law, not legal advice.

Sources