Please go back and learn the basic presumptions of the Constitution as explained in the Tenth Amendment. The power of the FEDERAL government are enumerated and delegated by the states and the people via the Constitution. If the power has not been delegated to the feds or prohibited from the states, the presumption of the Constitution is that power BELONGS to the states and the people.
Did you read my post?
I said what you said - Congress has not been granted the power to pass a law regulating marriages (except in DC and on Indian reservations and military bases), and the Constitution has not been amended to grant such a power, THEREFORE, it is a reserved power and THEREFORE the Supremacy Clause (Article VI §2) does not apply.