In a pivotal decision, the Supreme Court dealt a substantial setback to the Biden administration's environmental policies on Thursday. By a narrow 5-4 margin, the court suspended an EPA regulation aimed at mitigating interstate air pollution that contributes to smog formation. This ruling followed petitions from three Republican-led states—Indiana, Ohio, and West Virginia—and various industries, including natural gas pipeline operators, who argued that the regulation imposed undue burdens.

The regulation, known as the EPA's "good neighbor plan," targeted nitrogen oxide emissions from industrial facilities across 23 states, affecting air quality in neighboring states. Despite prior lower court rulings blocking the regulation in a dozen states, the Supreme Court's decision stands as a provisional win for opponents, with ongoing legal proceedings expected to shape its final outcome.

Environmental advocacy groups such as the Sierra Club and Environmental Defense Fund sharply criticized the decision, citing concerns over its immediate impact on public health. They warned that increased pollution levels could endanger millions of individuals, underscoring the critical need for robust air quality regulations.

West Virginia Attorney General Patrick Morrisey, a vocal opponent of the EPA's policies, welcomed the Supreme Court's ruling, arguing that the regulation could strain the power grid without sufficient regard for broader implications.

Writing for the majority, Justice Neil Gorsuch criticized the EPA's implementation approach, questioning the efficacy of enforcing the regulation selectively across different states. He highlighted deficiencies in the agency's cost-effectiveness analysis and raised doubts about its regulatory authority under the Clean Air Act.

Justice Amy Coney Barrett, often a pivotal figure in environmental litigation, dissented from the majority opinion, expressing skepticism about the legal basis for halting the regulation prematurely. She cautioned against preemptively suspending a significant air pollution rule before its full merits could be adjudicated.

The Supreme Court's conservative majority, known for its cautious stance on expansive federal regulatory powers, has consistently scrutinized the EPA's environmental policies. This skepticism has emboldened challenges from Republican state attorneys general and industry groups advocating for more restrained federal oversight.

This decision represents another setback for the Biden administration's environmental agenda, following previous Supreme Court rulings that curtailed the EPA's authority under both the Clean Air Act and the Clean Water Act. As legal battles continue and regulatory challenges persist, the future of federal environmental protections remains uncertain amid ongoing judicial and political contests.