The Federal Constitution has nothing to do with performing marriages. Only in recognizing documents and contracts issued in other states.
That is not true. Here is the law... pay attention to the red typeface.
Article IV.
Section. 1.
Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof.
Only Congress can define the effect by law...
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There is still the tenth amendment which is what I had in mind when I said the federal government has no jurisdiction over whether or not marriages can be PERFORMED. The Feds cannot make laws about performing homosexual marriage except for overseas jurisdiction/military etc. The Congress may only prescribe ways to proove whether a marriage license is valid if a state chooses to grant one.
Also not true... It was landmark U.S. Supreme Court precedent Reynolds v. United States in 1878 that made “separation of church and state” a dubiously legitimate point of case law, but more importantly; it confirmed the Constitutionality in statutory regulation of marriage practices...