Some things like pot they aren't really ignoring it. A state doesn't have to make something a crime that is already a federal crime. They can generally choose not to enforce federal crimes. They cannot refuse to assist federal law enforcement (though some red states are trying to do that on certain issues). But the feds can't issue a blanket order to a state's law enforcement saying "you have to enforce this federal law". They can only say something like "This ATF agent is working on a gun bust, and you need to help them".
Pot is reinforced because under Obama/Holder, they issued an order that the feds wouldn't enforce pot laws in states that decriminalized it with only limited exceptions. Frankly the stupidest part is the FDA could just delist it as a class 1 controlled substance and done. Leave it to the states.
So decriminalization of pot, for instance, isn't a state ignoring federal law. It is just choosing not to criminalize it themselves. Yes, they are also choosing not to arrest people for federal crimes, but that has never been a requirement on a state.
If a federal AWB passes, of course a state could ask for a stay until it works through the court system. I would expect some red state AGs to do just that, along with I am sure a large private party suit asking for the same. And it would likely be granted at the district court level, or at worst the appeals level.
