Read Reynolds vs the United States. Your argument is incorrect. Marriage has been federal since there’s been a US. The definition of marriage as one man and one woman was never left up to the states and Reynolds argues this is why the federal government could ban polygamy.
Arguing that ‘it’s not federal’ has opened the door for gay marriage in all 50 states. Congratulations.
Reynolds vs the United States, a court decision in 1879 will not sway the current majority of the court. Equal protection and yes, federal goodies has opened up that can of worms. DOMA was the last firewall against the sexual revolution. Just looking at the current situation, sorry.