I recently listened to the Supreme Court oral arguments in Loving v Virginia, the 1967 case that overturned anti-miscegenation laws. I took a lot of notes and wrote up my thoughts afterward, and here are some of the observations and reflections that resulted.
1. The Lovings' lawyer began by presenting the law they wanted declared unconstitutional, the reason the law was passed, and a little bit about its precursor laws, feeling no need at that point to present any criticism of any it, It was simply clear from his tone that he thought the reasons behind the law were thoroughly immoral. No justice questioned him on this, and it sure seemed to me that they tacitly agreed. I wasn't around at the time, but this seemed to me to be a good sign that by 1967 we'd moved far enough along already that everyone on the Supreme Court saw this law as despicable, morally speaking (which in itself doesn't settle the legal question, and thus they let the oral argument continue past this point).
2. When the Virginia attorney general got his turn, it didn't take long for him to refer to the Lovings' union as a marital relation. He never disputed that it was a marriage, just whether Virginia had authority to declare their marriage illegal. That's one clear difference between Loving v. Virginia and the same-sex marriage cases in the courts right now that we don't often see people drawing attention to. Those who favor laws banning interracial marriage were happy to use the word 'marriage' for those relations. They didn't think such a union wasn't a genuine marriage. They just thought such marriages should or at least could be banned without it violating anyone's constitutional rights. The issue of whether it would be a marriage simply didn't occur to them. It obviously was. On the other hand, that's precisely one of the key issues for same-sex unions. Whether they should count as marriages to begin with has been a crucial issue of controversy, and whether these laws therefore revise a longstanding definition of marriage, and whether a state can resist that, is therefore not an issue that came up under Loving v. Virginia. Those who say that Loving v. Virginia automatically settles such questions by the same reasoning have not recognized this. There are several ways that the arguments aren't parallel in every respect, and that's a noteworthy difference. If the arguments based on the parallel are going to prevail, then this difference ought to be shown to be legally unimportant.
3. Three lawyers argued on the Lovings' behalf. The third, William Marutani, on behalf of the Japanese American Citizens League, made an interesting vagueness point. He was arguing that it's impossible to determine whether someone is white by definition of Virginia law, according to which someone has to be purely white in having no non-white ancestors. The people we call white are of such mixed ethnic background in the melting pot of the United States (and in the European history among prior ancestors) that it's impossible to be sure with most people (at least the ones without good genealogical records) whether they are white according to the Virginia law. It's a good practical reason not to have such laws, even apart from the moral question. The opposing lawyer rightly pointed out that the Virginia statutes about those matters weren't being challenged, so by the rules of our legal system it's not really legally relevant unless someone challenged those statutes in the lower courts first. But I thought it was nice to see someone making that point as early as 1967. It's worth pointing out that he didn't make any mention of the even-more-mixed status of blacks, even at the time (but it's much stronger now, I'd wager), but that wouldn't have helped him except to challenge the definitions of terms used in the law according to how they're used in science or something like that, which is irrelevant to the law's constitutionality, since the law itself didn't make any difference for blacks according to how much black ancestry they had. All it took was a smidgeon.
4. The precise equal protection point is worth reflecting on. There was also a due process argument, but I don't pretend to understand how due process is supposed to work. I've never heard a due process argument that I've understood, for whatever reason. It's not that I understand what's being argued and disagree. I simply have no clue what's being argued with due process claims, and I've never gotten any clarity on that despite hearing lots of oral arguments, reading lots of opinions, and trying to wade through discussions in popular-level presentations. Due process rights, according to some (e.g. Justices Scalia and Thomas), is merely ensuring that the laws are followed and that no improper procedures are followed. I once agreed with this, but that makes it a vacuous claim to say that you can't pass laws that deprive someone of rights without due process of the law. You can't pass laws without ensuring that the law is really passed? Then I discovered that at the time the 14th Amendment was passed, there was much discussion of what's called substantive due process, which reads more into due process than the vacuous sort of view I've lost interest in defending. So when that part of the Constitution was framed, it may well have involved this notion of due process. Nonetheless, I can't make heads or tails of what due process is supposed to be on the substantive due process view or how one would argue that due process rights include some claimed right, other than reading one's own policy preferences into the notion, which I don't consider legitimate judicial practice.
But the equal protection claim is one I fully understand. Every person within a state's jurisdiction is guaranteed equal protection of its laws. If a law treats one person differently from another without a strong enough justification for doing so, then equal protection is violated. The Virginia attorney general conceded that there is no justification for his state's anti-miscegenation laws if all you had to go on were genetic and scientific issues. The only moral justification his state could have to pass such a law, in his view, is the harmful effects of interracial marriages on the children of such marriages and on the participants, and he concedes that these effects are because of the attitudes of the people of Virginia toward such unions and toward children of such unions. So it's a highly contingent claim, one that presumably (as far as he's argued) would not be present in a state without such attitudes.
That's another difference from the arguments of those who oppose same-sex marriage. Their arguments are not based on contingent factors about people's attitudes toward same-sex unions and people's attitudes toward children raised by those in same-sex unions (who are not possibly the product of those unions, to begin with, at least in the biological sense, although some might not exist but for those unions). Some of the arguments of those who oppose same-sex unions are based on statistical claims about marriage as traditionally conceived compared with same-sex unions when called marriages, and some of those (for all we know) might be contingent matters due to social circumstances. If no one opposed same-sex relations, these things might be different.
But not all the arguments are like that. Some have to do with the sociological conclusions of numerous studies showing that not only are two parents more valuable for the sake of the child than one but that having parents of both sexes tends to be better (other things being equal) for the children and having the child with biological parents (other things being equal) tends to be better for the child. So marriages as traditionally conceived will, apart from contingent matters like social attitudes, be better for the children, and thus there's a reason to encourage such unions by calling them marriages and not unions that don't have those features. Whatever the merits or demerits of such an argument are, it's a difference in the justifications used for preventing same-sex unions being called marriage and the justifications used for preventing marriages between those of different races, and that's rarely acknowledged in the arugments of those who think Loving v. Virginia's arguments apply exactly to the same-sex marriage cases. Those differences need to be dealt with for such arguments to go through.
5. I've long thought that the equal protection point itself isn't parallel, for reasons I explained here and here. I don't think I've changed my mind on that question since writing those posts, although I've realized that I need to look into some Supreme Court rulings in the 70s on equal protection and women to see if the sex-discrimination argument should work with the federal Constitution given current Supreme Court precedent. But I'm not going to get into the details of any of that here. This post is long enough already that I don't need to rehash what prior posts already covered or to predict what I might come to after listening to the arguments in those 1970s cases.