“Independent Substantive-Review” Requirement for EPA Approval of SIP Revisions
A Comprehensive Commentary on Center for Biological Diversity v. EPA (10th Cir. 2025)

1. Introduction

The United States Court of Appeals for the Tenth Circuit’s published decision in Center for Biological Diversity v. EPA, No. 23-9503 (Aug. 12, 2025), refines the procedural duties of the Environmental Protection Agency (EPA) when it approves State Implementation Plan (SIP) revisions under the Clean Air Act (CAA). The controversy centers on Colorado’s 2019 amendments to its SIP, which (1) tweaked permit-triggering language and (2) added an oil-and-gas specific clarification to the phrase “commencement of operation.”

The Center for Biological Diversity (CBD) petitioned for review, arguing that the revisions effectively loosen Colorado’s pre-construction controls by:

• Allowing construction to proceed before regulators analyze emissions (Issue 1).
• Excluding pre-production emissions from drilling, fracking, and well-completion activities (Issue 2).

The Tenth Circuit rejected the first challenge but sustained the second, holding that the EPA acted “arbitrarily and capriciously” by accepting Colorado’s assertion that the second change was merely “clarifying” without independently examining its substantive effects. The petition was therefore:

• Denied as to the revised permit-requirement wording.
• Granted as to the revised definition of “commencement of operation,” remanded for further EPA explanation, but without vacatur.

2. Summary of the Judgment

• Standing/Preservation: CBD’s objections were not waived; it had raised them with “sufficient specificity” during EPA rulemaking.
• Standard of Review: Administrative Procedure Act (APA) arbitrary-and-capricious review, 5 U.S.C. § 706(2)(A).
• Holding—Issue 1 (Permit wording): Changing “commence construction or modify” to “construct, operate, or modify” was stylistic. CBD failed to link any alleged permitting defect to the 2019 wording; therefore EPA approval was reasonable.
• Holding—Issue 2 (Commencement of operation): EPA uncritically adopted Colorado’s “clarification” rationale and failed to analyze whether the added clause carved out pre-production emissions. That constitutes arbitrary and capricious action.
• Remedy: Remand for further EPA consideration under Allied-Signal balancing; no vacatur; no deadline imposed, but CBD may later seek a § 706(1) unreasonable-delay action.

3. Detailed Analysis

3.1 Precedents Cited and Their Influence

• US Magnesium, LLC v. EPA, 690 F.3d 1157 (10th Cir. 2012) – Described cooperative federalism structure of the CAA.
• Espinosa v. Roswell Tower, Inc., 32 F.3d 491 (10th Cir. 1994) – Clarified that an approved SIP attains force of federal law; used to underscore disruptive consequences analysis.
• Ariz. Public Service Co. v. EPA, 562 F.3d 1116 (10th Cir. 2009) – Provided APA review standard and “important aspect of the problem” test.
• WildEarth Guardians v. EPA, 770 F.3d 919 (10th Cir. 2014) & Appalachian Power Co. v. EPA, 251 F.3d 1026 (D.C. Cir. 2001) – Framed preservation threshold (“sufficient specificity”).
• Allied-Signal, Inc. v. U.S. Nuclear Regulatory Comm’n, 988 F.2d 146 (D.C. Cir. 1993) – Two-factor vacatur test, adopted by the 10th Circuit in Diné Citizens v. Haaland, 59 F.4th 1016 (2023).
• Department of Homeland Security v. Regents of the University of California, 591 U.S. 1 (2020) – Cited for proposition that an agency may on remand supply fuller explanation, but courts review the contemporaneous rationale.

These precedents informed the court’s approach to:

• Determining whether EPA’s reasoning satisfied APA standards.
• Assessing whether CBD’s comments preserved the issue.
• Crafting the remedy (remand vs. vacatur).

3.2 Court’s Legal Reasoning

The opinion (Bacharach, J.) applied a methodological sequence:

1. Jurisdiction & Preservation: Invited-error doctrine rejected because CBD did not affirmatively endorse the challenged language in the state rulemaking.
2. Issue 1 Analysis (Permit wording)
   • Examined text before and after 2019 amendment; concluded substitution was semantic, not substantive.
   • Noted existing, separate provision already barred commencement without a permit, defeating CBD’s causation theory.
   • Therefore EPA’s “no-interference” finding under CAA § 110(l) was rational.
3. Issue 2 Analysis (Commencement definition)
   • EPA’s record showed it merely repeated Colorado’s assertion that the added sentence was “procedural.”
   • Such deference without independent inquiry ignored a potentially “important aspect of the problem”—the exclusion of pre-production emissions.
   • Thus, EPA’s approval was arbitrary and capricious.
4. Remedy Determination
   • Applied Allied-Signal factors: curability of error weighed in favor of remand; disruptive consequences uncertain.
   • Chose remand without vacatur, allowing the contested SIP text to remain temporarily effective while EPA re-examines.

3.3 Potential Impact on Future Cases and the CAA Landscape

• Heightened EPA Duty: Establishes a clear judicial expectation that EPA must perform an independent substantive review—not merely a “rubber stamp”—when states label SIP changes “clarifications.”
• Oil-and-Gas Sector Scrutiny: Signals courts’ willingness to scrutinize SIP language that could omit significant short-term emissions phases common in hydraulic-fracturing development.
• Remand-Without-Vacatur Trend: Reinforces the 10th Circuit’s measured approach in environmental cases, mindful of programmatic disruption yet insisting on procedural integrity.
• Citizen Comment Strategy: Underscores the value of focused but non-technical comments; perfect regulatory citations are not mandatory for preservation.
• Invited Error Boundaries: Clarifies that general support for a state’s rulemaking does not bar later federal-level challenges absent unequivocal endorsement of the precise disputed text.

4. Complex Concepts Simplified

• State Implementation Plan (SIP): A package of state laws and regulations the EPA approves to demonstrate how that state will achieve federal air-quality standards.
• National Ambient Air Quality Standards (NAAQS): Numerical pollution limits (for ozone, PM_2.5, etc.) that must not be exceeded in ambient outdoor air.
• “Potential to Emit”: A regulatory estimate of the maximum air pollutants a source could release assuming worst-case operation; drives whether a source is “major” or “minor.”
• Commencement of Operation: The legally defined moment a facility is considered operational for emission-calculation purposes. Colorado’s 2019 addition links this to when “product is consistently flowing” but no later than well completion—potentially overlooking earlier emission phases.
• Arbitrary and Capricious: APA standard requiring agencies to (1) examine relevant data, (2) articulate a rational connection between facts and decision, and (3) address important aspects.
• Remand Without Vacatur: A court sends a rule back to the agency for further explanation or fixing but leaves the rule temporarily in place to avoid disruption.

5. Conclusion

Center for Biological Diversity v. EPA crystallizes a vital procedural safeguard: the EPA must verify, not merely accept, a state’s assertion that SIP edits are non-substantive. Although the court upheld Colorado’s minor wording tweaks, it flagged the agency’s cursory acceptance of the new oil-and-gas commencement clause as legally insufficient. By remanding without vacatur, the Tenth Circuit balanced environmental protection against regulatory continuity, yet left a clear roadmap:

Practitioners should expect deeper EPA analyses of future SIP amendments, particularly those involving sector-specific carve-outs or definitional shifts. Citizen groups, meanwhile, can glean assurance that well-directed—but not hyper-technical—comments preserve their day in court. Ultimately, this decision reinforces cooperative federalism’s accountability: states may innovate, but the EPA must ensure those innovations faithfully protect national air-quality objectives.