If it is a natural right and is found to be protected then states cannot do so constitutionally. Conservatives are always like, "The constitution limits government to enumerated powers...and our rights are many and not all are mentioned in the constitution", right up until they agree/disagree with something. But then we've had many arguments about these things here. And there are a multitude of legal theories about it.
The courts job, in part, is to rule on matters of fundamental rights. If the court, right or wrong, rules that someone possesses a fundamental right, then the state may regulate to one degree or another, but they may not completely prohibit that right, especially when it does not infringe on the rights of another.
Essentially, marriage has long been ruled a fundamental right as much as having and raising children has also. The court said Alabama's law violates that fundamental right and order Bentley to stop enforcement of the state law, which is superseded by the fundamental right. Federal courts have this authority and if it is an overreach then congress has done nothing to regulate in the matter and would likely end up in another Marbury v Madison, in which case we'd end right back up at:
It is emphatically the duty of the Judicial Department to say what the law is. Those who apply the rule to particular cases must, of necessity, expound and interpret the rule. If two laws conflict with each other, the Court must decide on the operation of each.
If courts are to regard the Constitution, and the Constitution is superior to any ordinary act of the legislature, the Constitution, and not such ordinary act, must govern the case to which they both apply.
