The U.S. 5th Circuit Court of Appeals gave a big win to the EPA when it upheld a Biden-era ozone ruling affecting Louisiana and Texas, but there was also a set-back for the EPA when the Court both upheld the ability of such cases to be brought outside the D.C. Circuit, and reversed the EPA’s rejection of a Mississippi air quality plan. The case is State of Texas v. EPA.
Case Background
Under the Clean Air Act (CAA), states must develop state implementation plans (SIPs) that meet the law’s “Good Neighbor” requirement, which prevents states from contributing significantly to air pollution in downwind states. The EPA’s rejection of these SIPs allowed the agency to impose the now-paused federal Good Neighbor Plan (GNP) on 23 states. The case is one of more than 20 lawsuits across multiple circuits, with Texas, Louisiana, Mississippi, and industry groups challenging the EPA’s disapprovals as arbitrary, capricious, and inconsistent with the CAA.
The 5th Circuit’s Decision
Writing for the court, Judge Priscilla Richman denied petitions from Texas and Louisiana while granting Mississippi’s challenge, vacating the EPA’s disapproval of its SIP, and remanding the issue back to the agency. The panel included Judges Carl Stewart and Karen Gren Scholer, reflecting bipartisan judicial representation.
The court found that the Texas and Louisiana SIPs were deficient based on their own submissions, supporting the EPA’s disapprovals. However, it ruled that the agency’s rejection of Mississippi’s plan was unreasonable because it was based on updated air quality data that had not been available when the state prepared its SIP.
On the question of venue, the court dismissed the EPA’s argument that the SIP approvals were “nationally applicable” or had a “nationwide scope or effect,” which would require cases to be heard in the D.C. Circuit. This aligns with other court rulings and coincides with a U.S. Supreme Court case that appears to favor regional jurisdiction for such disputes.
The ruling comes amid broader legal battles over SIP approvals. For example, the 6th Circuit recently overturned the EPA’s rejection of Kentucky’s SIP. Meanwhile, the D.C. Circuit is awaiting a Supreme Court decision on jurisdiction before proceeding with cases concerning the EPA’s widespread disapproval of interstate ozone SIPs.
State Implementation Plans and EPA Authority
The 5th Circuit rejected Texas and Louisiana’s argument that the EPA’s role in SIP review is limited under the CAA’s cooperative federalism framework. Instead, the court upheld a broader interpretation of the EPA’s authority, emphasizing that states must do more than simply provide a “reasoned analysis” of their air quality plans—the EPA retains the power to independently assess whether SIPs meet the Clean Air Act’s requirements.
The Court also declined to rule on whether the Supreme Court’s 2024 Loper Bright Enterprises v. Raimondo decision, which ended the Chevron doctrine of judicial deference to agency interpretations, affects this case, stating that such a determination was unnecessary because the EPA’s rejection of Texas and Louisiana’s SIPs was justified based on the states’ own methodologies and data.
Texas and Louisiana had also challenged the EPA’s requirement that states follow the agency’s four-step framework for interstate ozone pollution assessment and apply a screening threshold of 1% of the National Ambient Air Quality Standard (NAAQS). Under the Trump administration, states could use a looser threshold of 1 part per billion (ppb), but the Biden and Obama administrations imposed the stricter 1% NAAQS standard, equivalent to 0.7 ppb. The 5th Circuit sidestepped these broader regulatory disputes by focusing on the EPA’s findings that Texas and Louisiana’s SIPs failed under their own terms.
Louisiana’s SIP
For Louisiana, the court rejected claims that the EPA dismissed key elements of the state’s SIP analysis—including back trajectory modeling, weather patterns, and wind rose data—without serious consideration. The court ruled that the EPA had reasonably evaluated these components and explained its technical concerns.
Texas’ SIP
Similarly, Texas’ SIP was rejected based on its own data and interpretation of the Good Neighbor Provision, independent of additional EPA modeling. The court found that the state’s plan did not meet statutory requirements even under its own framework.
Mississippi’s SIP
However, the court sided with Mississippi, ruling that the EPA’s use of updated 2023 air quality data—rather than the 2011 dataset available when the SIP was developed—was improper. Since Mississippi’s plan only exceeded the 1 ppb screening threshold under the new data, the court concluded that the EPA’s disapproval was “arbitrary and capricious.” Consequently, the court blocked the EPA from implementing a federal plan for Mississippi until the agency reassesses its SIP using appropriate data.
Conclusion
The 5th Circuit’s decision is a critical ruling that both upholds and constrains the EPA’s regulatory authority under the Clean Air Act. By affirming the agency’s rejection of Texas and Louisiana’s SIPs while overturning the disapproval of Mississippi’s plan, the court has established important legal precedents regarding the scope of EPA’s review powers, the use of evolving data in regulatory decisions, and the proper venue for legal challenges. The ruling highlights the continuing judicial and political tensions between federal environmental oversight and state autonomy in air quality management.
