The attorneys general of Nebraska and Oklahoma have asked the Supreme Court to declare unconstitutional Colorado’s law legalizing marijuana. The lawsuit states that, “The Constitution and the federal anti-drug laws do not permit the development of a patchwork of state and local pro-drug policies and licensed-distribution schemes throughout the country which conflict with federal laws.”

Many conservatives have criticized Nebraska and Oklahoma for being “fair-weather federalists” because their claims hinge, in part, on Gonzales...