This issue gets sticky in that the Supremacy Clause only applies to the 17 enumerated powers. The federal government is pretending it has the authority to regulate marriage, which they do not. So the Alabama may refuse to obey the federal ruling arguing that the states hold the power to make all rulings outside the specified realm of the federal government. Like it or not that is how our system was set up. Much of the power the federal government wields is not theirs and they only h ave it because We the People failed to tell them no.