The Supreme Court ended its term on Thursday with an important declaration: Using regulation as a shortcut to lawmaking will no longer fly. This limitation is long overdue. The shift emerged in the court’s decision in West Virginia v. Environmental Protection Agency, a highly anticipated environmental law case about the scope of the EPA’s authority to regulate carbon emissions. The court’s conclusion will impact not only emissions, but also regulation in many key policy areas of political and economic significance. The result may be a much-needed reinvigoration of Congress’s will to reclaim its legislative prerogative.