Seems to me the libertarian position would be to get the gov’t out of the institution of marriage, leaving it up to folks’ faiths. Gov’t involvement hasn’t been good for the institution of marriage, in my opinion. Like most thing gov’t is involved with, it eventually screwed it up.
Freegards
Civil Marriage has been the greatest invention of the last millennium! It has ensured that women and children, abandoned by unscrupulous men, are able to avail themselves of a legal, governmental resolution mechanism without resorting to familial retribution or falling into destitution. By providing legal protection of inheritance rights it has prevented much premeditated sexual/financial fraud and abuse within society. It's stabilizing force exerted on modern family life may very well be a major source of the economic growth of the last 500 years!