BTW, you are confounding two things here. It is and has been the rule of the Catholic Church that Catholics are to marry Catholics. That's true. However, that is part of the law of the Church, not the Natural Law. You can tell that because the Church can and does grant dispensations for Catholics to marry non-Catholics. Also, the Church recognizes the marriages of any two Christians to be sacramentally valid, and marriages between two pagans to be valid as well (though not sacramental).
But you absolutely cannot get a dispensation from the Catholic Church to marry someone of the same sex. Because that violates not just Church law which only pertains to Catholics, but also the Natural Law which pertains to everyone.
And on the interracial argument, the Catholic Church and I dare say most Protestant denominations never ever recognized the legitimacy of any American law that prohibited interracial marriage. Period. That was done by the state. Bans on interracial marriage never had any basis whatsoever in Natural Law and were therefore completely illegitimate from the date of their promulgation.
What I meant in my last post is that Western society has been continually redefining marriage for hundreds of years. The idea that marriage is and has always been a singular, stable idea is false.