Then stand by for legalized polygamy, polyandry, incest, statutory rape...
There are reasons why government regulates marriage and they're good ones.
Actually, the government doesn't regulate marriage, it simply chooses what to recognize. There is nothing that prevents Adam and Steve (and Fred) from dressing up in their whitest (who are they kidding?) frocks and having a day-long celebration in whatever way they want.
Including with snakes.
Except not on a plane.