There is no federal law on marriage anymore.
In 2013,the Supreme Court ruled the federal government must accept state definitions of marriage from states which allow homosexual marriages. The court ruled the federal government could not define marriage as a man and a woman. However, there was no replacement definition of marriage put in place.
So how can anyone refer to the federal definition of marriage overriding a state when there is no federal definition of marriage??? Or again, do we just make it up as we go along based on politically correct ideas???
Make it up as they go along and the federal Rat judges falling all over themselves to support homosexual marriage so they can use it on the resume for future moving up the judicial ladder.
I'll do you one better than that - Baker v. Nelson, a case in 1971 in which two sodomites in Minnesota sued the state when it refused to issue them a marriage license. They lost their case at the state level and then appealed to the SCOTUS. The SCOTUS received this case on mandatory appellate review, but refused to hear the case on the basis that there was no "substantial federal question." This is important because the fact that it was rejected on mandatory appeal means that they just punted the case, but that they were essentially rejecting the appeal on its merits - i.e. making a decision about the case.
They said that there was no federal question, essentially affirming that marriage is a state issue, and ONLY a state issue. This case also qualifies as a substantial ruling by the court, meaning that it is (in theory) controlling on all lower federal courts. In other words, all lower federal courts ought to be refusing to even rule on gay marriage challenges because they have ALREADY been overruled by the SCOTUS. There is no federal case for gay marriage supporters to make as it has already been rejected in 1971, and that is still where the matter sits.