The Supreme Court on Monday heard what could be one of the most consequential cases for climate change and clean air in decades, with Republican attorneys general and coal companies asking the court to strip the Environmental Protection Agency of its authority to regulate planet-warming gas emissions from power plants.

During oral arguments for West Virginia v. EPA, which lasted about two hours, not all of the court’s conservative majority appeared to be aligned with the petitioners, though some entertained the idea that the authority should be turned back to Congress.

The hearing came on the same day that a major UN-backed climate change report showed