Distinguishing Permissible Preemption from Unconstitutional Commandeering

For years, the preemption doctrine and the anticommandeering doctrine lived in an uneasy tension, with each threatening to consume the other. On the one hand, preemption permits Congress to insist that state law give way to congressional demands. On the other hand, the anticommandeering doctrine prohibits Congress from commandeering state legislatures or state executives. Without some way to establish a boundary between the two, preemption could swallow the anticommandeering doctrine by allowing Congress to control state law. Alternatively, absent some boundary, anticommandeering could swallow preemption by empowering states to refuse to be governed by the commands of federal law. Either the autonomy of the states or the supremacy of federal law would have to go