My friend Razi Hashmi sent me the link to this column arguing for marriage equality based on the principles of limited government.  The columnist rightly points out that the state interest in marriage is relatively recent and inappropriate.  It is also tainted by a racist past.  He writes:

As a matter of principle, the argument is charmingly simple: from where does the government derive the authority to prohibit consenting adults from marrying each other?

Though the word “traditional” has erroneously become attached to the concept, the state licensure of marriage contracts is not traditional in any sense of the word. State licensing regimes replaced church- and contract-based marriage only in the last few centuries, and are the byproducts of a sordid period of American history when governmentstook it upon themselves to prevent people of different races from marrying one another (licensing subsequently became a source of revenue generation for the same governments, which is why the practice continued even after the boogeyman of miscegenation was largely snuffed out).

In short, the state co-option of marriage was an exercise in massive government infringement on the natural rights of individual citizens, not a hearkening back to “traditional” values. Prior to that, marriage was widely considered a religious and contractual (i.e., a private) affair, not an institution of the state. For advocates of limited government who believe that the state has only the power to protect life, liberty, and property, it should be easy to condemn and oppose the racist, extortive practice of states usurping marriage regulation from churches and civil society.