On March 12, 2025, EPA Administrator Lee Zeldin announced the agency’s intention to reconsider 31 environmental regulations, describing the effort as the “single most impactful day of deregulation in EPA history.” While the scope of this initiative spans air, water, and climate regulations, the most consequential actions—legally and practically—center on a handful of cross-cutting programs and sector-specific rules.
Although the EPA’s announcement is styled as a deregulatory roadmap, none of the targeted rules are rescinded yet. Each proposed rollback will require full notice-and-comment rulemaking under the Administrative Procedure Act (APA), and legal challenges are inevitable. This GT Alert summarizes seven of the most significant rulemakings to watch and highlights the legal and procedural headwinds the EPA is likely to face.
Cross-Sectoral Rollbacks
Greenhouse Gas Endangerment Finding (2009)
The EPA’s plan to reconsider the 2009 Endangerment Finding (the “Finding”) threatens to upend the legal basis for regulating greenhouse gas (GHG) emissions under the Clean Air Act (CAA).1 The Finding, issued following the Supreme Court’s decision in Massachusetts v. EPA, required the EPA to determine whether GHGs “may reasonably be anticipated to endanger public health or welfare,” leading to regulation of CO₂ and other GHGs from mobile sources.2 The Finding concluded that six greenhouse gases, individually and in combination, contribute to climate change and pose a danger to public welfare.3 The EPA then applied the Finding more broadly to numerous stationary sources under its various CAA authorities.
Any move to revoke or materially alter this determination will face high procedural and evidentiary hurdles under controlling case law; any reversal must be supported by a well-reasoned explanation and contend with extensive factual records supporting both the original Finding and numerous other EPA rulemakings.4 In other words, it is likely to take EPA a fair amount of time to develop a package supporting a revocation of this finding.
Social Cost of Carbon (SCC)
The SCC, a key metric in regulatory cost-benefit analyses, has long been a focal point of legal and policy debate. The Biden administration set the SCC at $190 per metric ton of CO₂, significantly increasing the estimated benefits of GHG regulation and the costs of carbon-based sources of energy. The EPA now proposes to overhaul or potentially abandon the SCC, which could weaken the justification for existing and future climate-related rules.
This proposed shift, if implemented, could make it more challenging for agencies to justify the benefits of greenhouse gas regulations or mitigation measures required via Environmental Impact Statements (EISs). Plaintiffs may challenge the revision on grounds that it arbitrarily discounts intergenerational or global harm.5 Recent case law, including Missouri v. Biden, has addressed standing and the sufficiency of reasoning behind SCC-related decisions, suggesting courts are increasingly attentive to agencies’ cost-benefit frameworks.6 The SCC’s reevaluation also resonates with broader post-Loper Bright developments, requiring agencies to justify economic assumptions without the level of deference previously enjoyed.7
Enforcement Discretion and Termination of Environmental Justice (EJ) Programs
The EPA announced the closure of all “Environmental Justice and Diversity, Equity, and Inclusion arms of the agency” and a new posture on enforcement discretion—declining to prioritize actions not clearly tied to statutory mandates.8 Prior administrations have used enforcement actions to impose requirements via administrative consent orders that exceed regulatory requirements and to focus on enforcement of certain sectors. Although this aspect of EPA’s announcement is without much detail, the administration is likely to review and potentially change past enforcement practices and priorities.
Sector-Specific Rollbacks
Clean Power Plan Replacement (GHG Standards for Power Plants)
The EPA’s recent rule governing GHG emissions from existing power plants identifies carbon capture and storage (CCUS) as the “best system of emission reduction” (BSER) under Section 111 of the CAA.9 Reconsideration of the rule may focus on whether CCUS is “adequately demonstrated,” a required element of the BSER standard. Legal challenges could also invoke the Supreme Court’s decision in West Virginia v. EPA,10 which applied the major questions doctrine to restrict EPA’s authority to impose system-wide generation-shifting measures—raising questions about whether the Biden administration’s rule improperly shifted how electricity may be generated.
New Source Performance Standards for Oil & Gas (OOOOb/OOOOC)
These methane-centric rules apply to both new, and for the first time, existing oil and natural gas facilities.11 If the GHG Endangerment Finding is revoked or narrowed, the legal foundation for these rules could be undermined. Subpart OOOOc, which governs existing sources, establishes emission guidelines that specifically target methane, the primary greenhouse gas regulated under the rule. Although EPA currently limits the regulation to methane, its authority to do so derives from the broader Finding. If that Finding is reversed or weakened, Subpart OOOOc could be subject to legal challenge or rollback. A rollback could leave emissions regulation for a substantial portion of up- and midstream oil and gas infrastructure to individual states, creating a fragmented regulatory landscape.12
Subpart W – GHG Reporting Program
EPA’s greenhouse gas reporting requirements for oil and gas sources are closely tied to the Inflation Reduction Act’s methane fee, which remains a statutory requirement (although Congress voided EPA’s 2024 Waste Emissions Charge rule via the Congressional Review Act).13 Revisiting this (and other Greenhouse Gas Reporting Program requirements for other sectors) has already resulted in a legal challenge and raises uncertainty for obligated reporters.14 For example, on March 21, 2025, the Environmental Defense Fund filed a lawsuit challenging EPA’s extension of the Greenhouse Gas Reporting Program’s reporting deadline for 2024 data.15 EDF argues that the EPA unlawfully delayed the reporting requirements without public notice and comment, undermining the program’s role in providing vital information about pollution from major sources nationwide.
PM2.5 NAAQS and the Good Neighbor Plan
EPA’s reconsideration of the 2023 fine particulate matter (PM2.5) standards would have cross-industry implications, particularly for manufacturers and energy generators.16 The Good Neighbor Plan’s proposed reconsideration raises key issues for numerous industries and states dealing with cross-border ozone challenges, particularly given the most recent plan’s extension to non-power sector emissions.
This proposed reconsideration also coincides with ongoing litigation17 concerning CAA venue questions.18 On March 25, 2025, the Supreme Court heard oral arguments in Oklahoma v. Environmental Protection Agency, No. 23-106719, a case addressing whether challenges to the EPA’s disapproval of state implementation plans under the CAA’s “Good Neighbor” provision should be adjudicated in regional circuit courts or centralized in the U.S. Court of Appeals for the District of Columbia Circuit.
Oklahoma and other petitioners argued that the EPA’s disapproval of their state plans – designed to address interstate air pollution – should be reviewed in their respective regional circuits, as these actions were specific to individual states and localized regions. In contrast, the EPA asserted that because it used a uniform analytical approach and published the disapprovals collectively in a single Federal Register notice, the actions were nationally applicable and thus fell under the exclusive jurisdiction of the D.C. Circuit.
The Court’s decision in this case is expected to clarify the appropriate judicial venue for such challenges, which could impact how states and industries address issues and frame arguments on reconsideration of the Good Neighbor Plan.
GT Insights
While EPA’s announcement carries no immediate legal effect, its significance lies in the number and breadth of proposed changes and the foundational rules it seeks to reconsider. Each reconsideration will be subject to APA requirements, including proper scientific and economic justification, public comment, and interagency review, all of which will take time to undertake. Moreover, litigation is almost inevitable. Courts may apply heightened scrutiny notwithstanding Loper, particularly where the EPA departs from prior factual findings or statutory interpretations.20
Regulated entities should prepare for a prolonged period of legal and regulatory uncertainty at the federal level. Active participation in the reconsiderations’ public comment processes, submission of technical and economic data, and strategic litigation positioning will be essential in shaping the next phase of environmental policy.
1 42 U.S.C. § 7521(a)(1). See also 42 U.S.C. §§ 7470–7492, 7661–7661f (provisions for the PSD and Title V permitting programs).
2 Massachusetts v. EPA, 549 U.S. 497 (2007).
3 Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act, 74 Fed. Reg. 66,496 (Dec. 15, 2009).
4 Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 42 (1983). See also Ethyl Corp. v. EPA, 541 F.2d 1 (D.C. Cir. 1976) (en banc) (discussing precautionary principles in environmental regulation); Chevron U.S.A. Inc. v. Nat. Res. Def. Council, 467 U.S. 837 (1984).
5 EPA, Technical Support Document: Social Cost of Carbon, Methane, and Nitrous Oxide – Interim Estimates (Feb. 2024).
6 Massachusetts v. EPA, 549 U.S. 497 (2007).
7 Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 42 (1983). See also Ethyl Corp. v. EPA, 541 F.2d 1 (D.C. Cir. 1976) (en banc) (discussing precautionary principles in environmental regulation); Chevron U.S.A. Inc. v. Nat. Res. Def. Council, 467 U.S. 837 (1984).
8 See Missouri v. Biden, 576 F. Supp. 3d 622, 635 (E.D. Mo. 2021) (addressing standing to challenge SCC metrics).
9 Heckler v. Chaney, 470 U.S. 821, 831–32 (1985).
10 Control of Air Pollution From Existing Stationary Sources: Electric Utility Generating Units, 88 Fed. Reg. 33,692 (May 23, 2023).
11 West Virginia v. EPA, 597 U.S. ___, 142 S. Ct. 2587 (2022).
12 Standards of Performance for Crude Oil and Natural Gas Facilities for Which Construction, Modification, or Reconstruction Commenced After November 15, 2021, and Emissions Guidelines for Crude Oil and Natural Gas Facilities for Which Construction, Modification, or Reconstruction Commenced On or Before November 15, 2021, 88 Fed. Reg. 74,406, 74,408–10 (Nov. 29, 2023) (to be codified at 40 C.F.R. pts. 60, 62) (“EPA is finalizing GHG emission guidelines for methane from existing sources … These actions are based on the 2009 Endangerment Finding for greenhouse gases.”); Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act, 74 Fed. Reg. 66,496 (Dec. 15, 2009).
13 42 U.S.C. § 7411(d).
14 26 U.S.C. § 136(f)(5) (Inflation Reduction Act methane fee).
15 Environmental Defense Fund v. U.S. Environmental Protection Agency, No. 25-1056 (D.C. Cir. filed Mar. 21, 2025).
16 42 U.S.C. § 7414(a).
17 See 42 U.S.C. § 7607(b)(1) (CAA venue provisions).
18 National Ambient Air Quality Standards for PM2.5, 89 Fed. Reg. 12,844 (Feb. 7, 2024).
19 Transcript of Oral Argument, Oklahoma v. Envtl. Prot. Agency, No. 23-1067 (U.S. Mar. 25, 2025).
20 Motor Vehicle Mfrs. Ass’n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 42 (1983). See also Ethyl Corp. v. EPA, 541 F.2d 1 (D.C. Cir. 1976) (en banc) (discussing precautionary principles in environmental regulation); Chevron U.S.A. Inc. v. Nat. Res. Def. Council, 467 U.S. 837 (1984).