The U.S. Supreme Court on Monday refused to review a challenge to the Environmental Protection Agency's authority to allow California to set its own greenhouse gas emissions standards for vehicles, leaving intact a D.C. Circuit decision upholding the EPA’s waiver under the Clean Air Act.

The denial, issued in a brief order with no explanation, ends a push by red states to overturn California’s unique authority to impose stricter vehicle emissions rules. Justice Clarence Thomas indicated he would have granted the petition.

States’ Challenge to California’s “Special Status”

Ohio and 16 other states argued that the EPA’s practice of granting California waivers to establish independent emissions standards violated their constitutional right to "equal sovereignty." In a July petition for writ of certiorari, Ohio said the Clean Air Act improperly “elevated California above all the other states” by granting it unique regulatory powers.

Congress included the waiver provision in the Clean Air Act decades ago, recognizing California’s leadership in regulating vehicle emissions. The EPA has issued such waivers consistently, including in 2022, enabling California to implement stricter greenhouse gas standards and zero-emission vehicle mandates.

The D.C. Circuit rejected the states' arguments earlier this year, finding that many of their claims lacked standing and that the others failed on the merits. Fuel industry groups also challenged the waiver, but the D.C. Circuit similarly ruled they lacked standing.

California Defends Its Leadership

California, backed by a coalition of blue states, defended its authority, citing Congress’ history of tailoring federal laws to meet specific state conditions. The state argued that Congress has long treated states differently in areas such as land management and regulatory histories, particularly when commercial and environmental conditions warrant.

“The nature of the commerce power... presupposes Congress’ authority to adjust preemption based on particular states’ commercial conditions or regulatory histories,” California said in a brief.

The EPA argued that Congress' decision to grant California waivers reflects the state's pioneering role in emissions regulation, which has often set the stage for broader national standards.

Broader Implications

While the Supreme Court declined to hear the red states’ challenge, it agreed to review a separate aspect of the D.C. Circuit’s ruling related to standing for fuel industry groups. This could shape future litigation over federal environmental waivers and the Clean Air Act.

Legal Representation

• States Challenging the Waiver: Represented by their respective attorneys general.
• EPA: Represented by U.S. Solicitor General Elizabeth B. Prelogar and attorneys from the U.S. Department of Justice.
• California and Supporting States: Represented by their attorneys general.
• Fuel Industry Groups: Represented by Jeffrey B. Wall of Sullivan & Cromwell LLP and others from Sidley Austin LLP, Bracewell LLP, and Pillsbury Winthrop Shaw Pittman LLP.

The Supreme Court’s decision leaves California’s emissions authority intact for now, reinforcing the EPA’s long-standing waiver practice under the Clean Air Act.