During oral arguments over the repeal of Proposition 8, Justice Antonin Scalia asked the following question of Ted Olson, one of the attorneys arguing for the repeal: "I’m curious, when—when did—when did it become unconstitutional to exclude homosexual couples from marriage? 1791? 1868, when the Fourteenth Amendment was adopted?" Mr. Olson's answer was rather labored and tentative. To paraphrase his reply, he asserted that this change had happened at some indeterminable point when society realized that sexual orientation is not a matter of choice. Not being a lawyer, I am not aware of the possible legal reasons behind Mr. Olson's evasiveness. Still, I can not help expressing dissatisfaction with this answer.
From my perspective, the answer to Justice Scalia's question is quite clear: denial of marriage equality became unconstitutional with the adoption of the Fourteenth Amendment and its guarantee to all citizens of "the equal protection of the laws." There is no network of legal obligations in which a citizen is enmeshed so binding or significant as the family, and there is no familial relationship more intimate than with one's spouse. This latter fact is a function of U.S. law, and may be deemed a hallmark and prime achievement of our American Revolution. In the Old World the obligations borne to one's natal family trumped that to one's spouse (blood was, as they said, thicker than water). In America, one's spouse became one's next-of-kin, because we recognized that weight should be given to the one family relationship that was entered into freely and of one's own volition. In a democracy, choice trumps birth.
Anyone excluded from the marital compact is deprived of this ability- the power to choose one's closest relative. Given that under federal law alone, marital status conveys 1,138 rights and benefits, anyone barred from the institution of marriage can not possibly be said to enjoy "the equal protection of the law." Unless one is willing to completely discount the role of love in family life, there is no way to square the denial of marriage equality with the imperative of the equal protection clause.
Putting a date on this change is less paradoxical that it may sound. We should not confuse the time when a law became unconstitutional with the point at which it "became" wrong. It was always wrong to deny human beings the equal protection of the law on the basis of race. The fact that it only became unconstitutional and illegal in 1868 did not make it any less wrong in 1791. On the same principle, the exclusion of same-sex couples from marriage always denied them the equal protection of the law. The fact that we are only realizing it now did not make it any less unconstitutional in 1868. The constitution is not a guide to right or wrong, it is a set of rules by which the organs of our government are bound. As our understanding advances, the implications of those rules change. Now that we know that marriage discrimination deprives millions of our citizens the equal protection of the law, we are bound by our own constitution to the establishment of marriage equality.