Greece and Rome, and Indian tribes, and head hunter tribes, and everyone, have always had marriage law, whether it was called just law, or the law of the official religion that made marriage law.
Naturally, there were pissing matches between the courts. At some point in the not so distant past, these separate courts were merged.
My point being only that "marriage has always been recognized under the law" misses the fact of historical separation of courts.
I was taught that if you didn’t get married by a priest/minister/rabbi, etc of your faith, before God you were not married, but only involved in a civil contract-I was raised in a traditional Catholic family-I understand that thinking is considered passé by a lot of people, but is still what I believe-and no way would I go to some apostate priest to get married who performed the ceremony for anyone/anything but one man and one woman.