Under the Supreme Court’s preemption doctrine, federal agencies may preempt state law in much the same way that Congress can. While the Supremacy Clause clearly empowers Congress to preempt state law, administrative preemption rests on the undertheorized assumption that Congress may “delegate supremacy” to agencies. This Article challenges the constitutionality of that premise and offers a normative defense of a federalist system where agencies are stripped of the power to create supreme law. My proposal to foreclose administrative supremacy will no doubt be controversial because of the significant implications it creates for federalism and the operation of modern government. Some of the more serious implications would include a state’s ability to trump conflicting agency policies (rather than vice-versa) and potentially requiring Congress to decide more preemption questions than it might reasonably be expected to. This Article argues that these and other implications are not only more consistent with the framers’ original design but, on balance, may better promote the values of federalism.