Here in Alabama it would not be law enforcement refusing, but the entire state government.
The state would declare such a national law null and void, and go to court against it on the Constitutionality given the 2nd Amendment. In the meantime, they would pass a law forbidding armed confiscation of any kind.
In fact, let me check, but I think we passed such a state law a few years ago...
This state is rated the most conservative in the USA, and I don’t think that will change much over the next several decades. And usually, with the exception of Doug Jones who beat a damaged and embattled Roy Moore by depressing the conservative desire to vote, there aren’t enough blacks and white liberals to elect a state-wide democrat.