One disappointment on a remarkable day: It's too bad that no Justice in the Obergefell majority saw fit to make a serious equal-protection argument.
There are of course at least two straightforward equal-protection arguments that could have been endorsed. One would regard laws limiting marriage to same-sex partners as denials of equal protection to non-heterosexuals. The other would regard such laws as simple sex discrimination. If a man wants to marry a man and is denied a license for doing so, but would have been granted the license had he been a woman, he is discriminated against on the basis of his sex, plain and simple. So such laws must get heightened scrutiny like all other laws that classify and discriminate on the basis of sex.
I have always considered the sex-discrimination argument compelling, both doctrinally and as a way of capturing what is deeply at stake in same-sex marriage.
Doctrinally, it always seemed to me stronger than either a substantive due process argument (because tighter and less subjective) or an argument about discrimination on the basis of sexual orientation (because of the automatic ascent to heightened scrutiny). To be sure, many advocates for same-sex marriage have disfavored the sex-discrimination argument, in part because it does not map the specific project of liberation and recognition for people of non-heterosexual orientations. That is, from a certain perspective, the sex-discrimination argument asks people in same-sex relationships to "cover" their distinctive sexual identities by folding their claim into one that need not name categories beyond "men" and "women." But it is not clear that that concern, legitimate as it is on its own terms, should be dispositive. Constitutional law does not always deliver the goods in exactly the way each plaintiff might want. We are entitled to due process and equal protection; we are not always entitled to recognition in the particular terms that we would find most resonant.
What's more, the sex-discrimination argument has the important virtue of placing the same-sex marriage issue in a deep and broadly applicable context. The major revolution driving much of modern equal protection law is the attenuation of the traditional practice of assigning people to social roles on the basis of characteristics that are inborn, inherited, or otherwise highly resistant to change -- race and sex centrally among them. The rise of same-sex marriage is a salient manifestation of that development. It says that people will not be assigned to particular roles within marriage by virtue of their sex, thus reflecting in a core location for sex roles the idea that people cannot be assigned to social roles more generally on that basis. Given the place of marriage in the traditional sex ordering, if government cannot assign roles in marriage on the basis of sex, then where can government assign roles on that basis? Pretty much nowhere, and that's the point. If that idea is deeply internalized, a great deal of liberation and equality for LGBTQ persons follows as a matter of course.
It may not be surprising that Justice Kennedy gave short shrift to equal protection. But it is disappointing that none of the Justices who joined him bothered to make the equal protection argument. It lets the dissenters fail to engage with a doctrinally tighter argument for today's result--one that does not invite either ripostes or good-faith worries about plural marriage, or negative liberty, or Lochner v. NY. More fundamentally, the omission of a strong equal-protection argument hides a satisfyingly rich explanation for why equal treatment of same-sex and opposite-sex marriages is a necessary aspect of modern constitutional law more generally.
I do not pretend to know the inside dynamics of the Court here, but I find it hard to believe that a separate opinion on equal protection grounds would have risked the majority in today's decision. Justice Kennedy was going where he was going. Nor do I see how untoward doctrinal consequences would have followed even if a separate opinion on equal protection grounds had refused to endorse Justice Kennedy's due process rationale and therefore created a holding without a majority. So I am left to wonder, and to lament. On an otherwise remarkable day.