(a) As the Tenth Amendment confirms, all legislative power not conferred on Congress by the Constitution is reserved for the States. Absent from the list of conferred powers is the power to issue direct orders to the governments of the States. The anticommandeering doctrine that emerged in New York v. United States, 505 U. S. 144, and Printz v. United States, 521 U. S. 898, simply represents the recognition of this limitation. Thus, "Congress may not simply ‘commandeer the legislative process of the States by directly compelling them to enact and enforce a federal regulatory program.’ " New York, supra, at 161. Adherence to the anticommandeering principle is important for several reasons, including, as significant here, that the rule serves as "one of the Constitution’s structural safeguards of liberty," Printz, supra, at 921, that the rule promotes political accountability, and that the rule prevents Congress from shifting the costs of regulation to the States. Pp. 14–18.