The Supreme Court has struck down the Environmental Protection Agency’s rule limiting the amount of mercury and air toxics emitted by coal- and oil-fired power plants, finding that the agency acted unreasonably in failing to consider the cost of the regulation. Michigan v. Environmental Protection Agency, No. 14–46 (June 29, 2015). The Court ruled that a statutory mandate that the regulation be “appropriate and necessary” encompassed cost considerations, and that it was not “‘appropriate’ to impose billions of dollars in economic costs in return for a few dollars in health or environmental benefits.” Read our full Update here.