Whenever we publish something about an anti-commandeering-style nullification bill, somebody inevitably responds with something along these lines. “I’m not a lawyer, but doesn’t federal law supersede state law?”
In short, the answer to that question is no.
In fact, the Supremacy Clause doesn’t even apply when it comes to anti-commandeering.
Anti-commandeering laws merely prohibit the use of state resources or personnel for the implementation of enforcement of federal acts or regulations. This approach does nothing to block federal enforcement, nor does it claim to alter the law. It merely denies the federal government state support.
Although under the Supremacy Clause, federal laws passed in pursuance of the Constitution stand superior to state laws (In other words, only in areas where the they feds are delegated authority.) there is no requirement that states enforce them. Ultimately, the federal government must enforce its own acts. States can participate if they want to, but they can also legitimately refuse to do so.
Anti-commandeering legislation takes advantage of this constitutional truth.
Rather than direct action against federal laws, acts or regulations, anti-commandeering is simply a lack of any state action whatsoever. When the feds come around to enforce their laws or implement their programs, the states just stand back and shove their hands in their pockets, so to speak. What makes this tactic so effective is that in practice the feds are utterly reliant on the states to enforce their laws. When the states withhold their help, the federal laws lose their teeth.
Anti-commandeering leads to nullification in effect, but it is carried out in an indirect manner. For example, states can refuse to assist the feds in carrying out raids in order to enforce federal drug laws. Without state assistance, the feds can’t carry out as many raids – if any at all. As a result, the law is not enforced as vigilantly – if at all. The federal law remains on the books, but it is not enforced in practice.
James Madison advocated this tactic, writing in Federalist #46 that if the people in a state were opposed to “unpopular” federal laws, even constitutional ones, they had the ability to undermine them by a refusal to cooperate.