In a blow to the Obama administration’s efforts to combat climate change, the Supreme Court has temporarily blocked regulations to limit emissions from coal-fired power plants. The stay comes as an appeals court considers a challenge to the rules brought by corporations and 29 states. The Supreme Court’s decision to halt the rules is reportedly unprecedented—the court has never before agreed to block a regulation before it’s been reviewed by a federal appeals court. The move indicates the Supreme Court is likely to overturn the regulations in the future. The decision could imperil the Paris climate accords, since the coal plant rules formed a key part of the U.S. commitment to cut emissions.