During the morning hearing, Patrick Morrisey, the attorney general of West Virginia, led off the speakers, saying that the power plan “is not only unlawful, but it’s bad policy as well.” He led the coalition of states that sued to stop the power plan. The Supreme Court in February delayed enforcement of the regulation. (In similar fashion, a number of Democratic state attorneys general, including Maura Healey of Massachusetts and Eric T. Schneiderman of New York, have pledged to fight the repeal in court.)

Robert E. Murray, founder and president of Murray Energy, a major coal producer, exulted, “In President Trump, we finally have a president who has vowed to preserve coal jobs.” The Obama administration’s rule, which he called the “so-called and illegal Clean Power Plan, better known as the no-power plan,” would impose “massive costs on the power sector and American consumers” while eliminating even more coal jobs.

Before the hearing began, Mr. Murray warmly greeted dozens of miners whom his company brought in by bus for the event. “You all know you have to work the afternoon shift now,” he joked.

Several groups are also holding an alternate hearing across the Kanawha River, at the University of Charleston, to discuss the environmental, health and climate benefits of reducing coal consumption. “The Clean Power Plan has a lot of support,” said Bill Price, a local organizer for the Sierra Club who grew up in the area and whose father worked in the coal mines. Since the shift to power sources like solar and wind create jobs and clean the environment, he said, the Clean Power Plan is “pro-worker, pro-economy and it’s pro-environment.”