[Steel Wolf]

Marriage without government would be a contract between two individuals, and one of the few proper roles of government is enforcing contracts.

Marriage doesn't exist without some form of authority to make it exist. It is not an individual act that exists without some kind of government.

Find me a society that has marriage, and I'll show you a tribe, nation, or belief system.

[mvpel]

So really the question becomes "whose authority," and who recognizes that authority.