In a rare defeat for the U.S. Environmental Protection Agency, the U.S. Supreme Court ordered it on Monday to reconsider whether the EPA’s regulations on mercury and other toxic emissions from power plants are appropriate and necessary. While the EPA considered the costs and benefits of various regulatory options later in the rule-writing process, the court faulted it for not considering compliance costs at the beginning to determine whether regulation was appropriate in the first place. The ruling is unusual because so far the federal courts, including the high court, have been deferential to the EPA’s attempts to write ambitious rules to curb pollution from power plants. While the courts have become increasingly aggressive in invalidating regulations issued by other federal agencies, the EPA’s air pollution regulations have mostly survived judicial scrutiny. Starting with “Massachusetts versus EPA” in 2007, the Supreme Court has repeatedly upheld the EPA’s authority […]