you can't give states this right, while at the same time having the SCOTUS toss the federal defense of marriage act (which they will do when given the chance).
so what do you do, absent a constitutional amendment?
If you're inclined for a research project..suggest you look up the quotes of Dem Senators who were in the senate when the ERA last came up for a vote..
Nothing. Let them get married. This country has more important things to worry about.