Alright, let me ask you this: is there any area of life that the government should not control?
Some facts, the argument to remove any legal definition of marriage would be the end of marriage anyway, since it wouldn’t exist and the word would not have any definition at all.
Besides, government or a controlling religion/authority has always had to rule on marriage, society cannot function without it, that is why the Romans, the Greeks, the Apache, New Guinea headhunters, people that we have never heard of, all had to have marriage laws, property, children, inheritance, warrior deaths in service, marriage law is not something that politicians cooked up a 100 years ago.
Besides, why waste time on such childish LIBERTARIAN silliness anyway. DON’T WASTE TIME IGNORING ACTUAL POLITICS AND REAL LIFE AND CURRENT LEGISLATION AND ELECTIONS BY TRYING TO PRETEND THAT MARRIAGE WILL BE REMOVED FROM LAW AND GOVERNMENT IN THE NEXT YEAR OR TWO OR 20 ANYWAY, THAT ARGUMENT DOESN’T EXIST, AND QUIT PRETENDING THAT IT DOES.