There's a concept called "preemption" in US law. If a state and the federal government has laws that conflict, federal law wins and the state's law is voided. What this means is that if the federal government wishes to regulate something, it can direct that the states' regulations are circumscribed or voided.

The FCC first tried to regulate net neutrality, but that was struck down by a court as beyond its remit, since ISPs weren't common carriers. So the FCC declared that ISPs were in fact eligible for Title II regulation, which effects preemption of state-level regulations. Except the current administration has had the FCC declare that ISPs are not Title II carriers, and therefore FCC has no right to regulate them... which makes it difficult to argue that the federal regulations (which no longer exist) can preempt state regulations.