California Attorney General Rob Bonta and the California Air Resources Board led a multistate coalition intervening to defend the EPA rule. The court confirmed the EPA's authority to regulate soot based on scientific evidence of public health risks. The standard remained in effect throughout the litigation.
The Trump Administration EPA has not implemented the 2024 standard despite the court's validation, prompting Bonta and CARB to file a separate lawsuit against the federal agency for non-compliance. The EPA's 2024 analysis projected the standard would prevent 4,500 premature deaths annually and generate $46 billion in net health benefits.
Attorneys should monitor the ongoing enforcement litigation against the Trump EPA. The court ruling eliminates legal uncertainty about the standard's validity, but implementation remains contested. The case exemplifies the emerging pattern of state-level enforcement actions challenging federal regulatory inaction on environmental rules.