But I just thought of an example:
Let's say you want to build a car. Pretend long ago, your state passed a law that says you can build as many cars as you want any way you want to. Can you build a car? NO. Why? Because the federal government has since passed legislation in that area to the extent that it is clear that they have decided to usurp all state legislation regarding car manufacture. Now, if you want to build a car, you have to have permission from the federal government, even though car building was previously, before the federal laws were enacting, clearly regulated at the state level. So let's say your state passes a brand new law, again saying you can build cars. Can you do it now? No. Why? Same reason: "Because the federal government has since blah blah blah...."
This principle of constitutional law is FIRMLY established, and has been for something like eighty years.
Here's another example: Remember Drive 55 Stay Alive? There was no evidence it saved lives. There was plenty of evidence to the contrary. Before 1974, the states set the speed limits. Congress decided to take over in 1974 and passed 55. Could the states pass new speed limit laws? Sure. Would new state speed limit laws have any effect? Nope. EVERYBODY GOT SCREWED and there wasn't a damn thing anyone could do about it for 20 years until we turned over congress in 1994, and they repealed the law.
There is NO DIFFERENCE here.