Digging at the Roots — Federal Environmental Rulemaking Rollbacks

Originally published for customers May 27, 2026.

What’s the issue?

The Trump administration is narrowing federal environmental authority across air, water, and wildlife regulation through overlapping rulemakings.

Why does it matter?

Any one of these initiatives could result in fundamental regulatory shifts, but tracking them is increasingly difficult because many are simultaneously being rewritten, delayed, and litigated.

What’s our view?

These federal environmental rulemaking rollbacks differ from prior initiatives because agencies are increasingly arguing the statutes never authorized some of these broader regulatory interpretations in the first place.

The Trump administration is pursuing overlapping federal environmental rulemaking rollbacks across three areas of law — air quality, water jurisdiction, and wildlife protection. In each case, agencies are arguing that statutes never authorized the broader regulatory interpretations that prior administrations relied on. Arbo previously examined EPA’s proposed repeal of the Greenhouse Gas Endangerment Finding and its methane implications in Second Bite at the Bench? EPA’s Endangerment Rollback and the Methane Map for Pipelines; since then, additional developments across all three environmental domains have further clarified the administration’s approach. The table below summarizes where each major rulemaking stands.

Air Quality Rulemakings: Endangerment Finding, Methane Rules, and GHG Reporting

EPA’s Endangerment Finding Repeal

EPA’s proposed repeal of the Endangerment Finding is the clearest example of this shift. While the original Finding technically applied to motor vehicles, it became the legal foundation for a much broader greenhouse gas regulatory structure, including methane rules affecting the oil and gas sector. Its proposed repeal would remove the statutory basis underlying that entire framework.

EPA’s Methane Rule — Litigation Tracks and Flaring Exemptions

The Biden administration’s methane rules established emission limits, leak detection and repair requirements, and other standards for oil and gas infrastructure. At least eleven D.C. Circuit challenges followed — brought by both environmental and industry petitioners — and the cases have been mostly held in abeyance after the Trump administration announced reconsideration. For a current read on where those cases stand alongside other gas infrastructure disputes, see Arbo’s Q2 Quarterly Gas Infrastructure Litigation Update.

The litigation was divided into three tracks: environmental petitioners, industry petitioners, and a separate track for the American Petroleum Institute (API). The API track focused heavily on flaring and monitoring requirements. EPA subsequently issued a rulemaking that relaxed temporary flaring limits for associated gas from new sources and significantly expanded exemptions from continuous monitoring requirements for certain flares and combustion devices; EPA stated that industry argued a 72-hour flaring window was “more appropriate” than the agency’s earlier proposal.

Critically, this most recent rulemaking did not address how the proposed repeal of the Endangerment Finding could apply to the methane rules. That broader question remains unresolved and will likely become part of the larger litigation landscape once paused methane cases resume.

GHG Reporting Program Reconsideration

EPA is also reconsidering the Greenhouse Gas Reporting Program. In September 2025, EPA proposed rescinding portions of the reporting framework while revising reporting obligations under other Clean Air Act authorities. That reconsideration is already affecting implementation timelines: EPA recently extended the reporting deadline for reporting year 2025 from March 31, 2026 to October 30, 2026 while the agency evaluates broader revisions. EPA received more than 50,000 comments on the proposal.

Wildlife: Narrowing the ESA Definition of “Harm”

A parallel narrowing effort is underway under the Endangered Species Act of 1973. In April 2025, the U.S. Fish and Wildlife Service and National Marine Fisheries Service proposed rescinding the regulatory definition of “harm.” Historically, agencies interpreted “harm” broadly enough to include habitat modification that indirectly injures protected species. The proposal argues that interpretation exceeds the best reading of the statute, leaning heavily on Loper Bright Enterprises v. Raimondo to contend that “take” historically referred to actions directed immediately and intentionally against a particular animal, not indirect habitat impacts affecting populations more broadly.

No final rule has been issued. If finalized, a narrower interpretation could materially reduce future project exposure to prohibited take claims and potentially limit the scope of mitigation requirements in both Section 7 consultations and Section 10 incidental take permitting. At the same time, removing the regulatory definition without replacing it may create additional litigation uncertainty over how courts interpret the statutory term “take” going forward.

Water: WOTUS Jurisdiction and Section 401 Certification

Arbo previously examined the ongoing Section 401 and WOTUS reform landscape in Section 401’s Endless Reset Button — and the Push to Fix It. Those rulemakings remain unresolved but continue moving forward. For how a pending legislative fix could reshape Section 401 permitting timelines, see Arbo’s post on the Unlock Act Could Reshape Section 401 Pipeline Permitting.

On the jurisdictional side, EPA and the Department of the Army proposed a new WOTUS rule intended to fully implement the Supreme Court’s decision in Sackett v. Environmental Protection Agency, which would further narrow which waters qualify as federally regulated under the Clean Water Act. Separately, EPA proposed revisions to the Section 401 water quality certification regulations earlier this year; public comments closed in February 2026. As of May 2026, no final rule has appeared at the Office of Information and Regulatory Affairs dashboard for either rulemaking.

Like the Endangerment Finding and ESA “harm” proposal, these are not simply procedural revisions — they are attempts to narrow the scope of federal jurisdiction itself. Their interaction with active pipeline permitting timelines is one of the key variables Arbo continues to track. For how permitting reform is affecting project construction schedules more broadly, see From Paper to Pipe, What Recent Reforms Mean for Project Timelines.

If you would like to discuss how shifting federal environmental rulemaking rollbacks and related litigation could affect permitting timelines, compliance obligations, or project risk exposure, please contact us.