The role of government in marriage licensing is a critical part of the discussion of same-sex and other kinds of marriages which is often overlooked. Is government's granting of marriage licenses to gay couples, or to polygamous partnerships, entail a moral approval of those relationships. Robert George argues yes, here.
Yet, clearly our government does give marriage licenses to people whose relationships do not pass any kind of moral test. For example, the government has no qualms in giving licenses to couples who began their relationships in adulterous affairs.