The Ninth Circuit has overturned Proposition 8 in California, which reinstated a ban on same-sex marriage as part of the California Constitution when the California Supreme Court had interpreted the California Constitution as requiring the state to issue marriage licenses to same-sex couples seeking them. Eugene Volokh has one of the better explanations of the reasoning that I've yet seen (but I haven't looked around too much yet). I have two immediate thoughts:
1. It seems clear that the Ninth Circuit is using a rational basis test, which is the strongest test the Supreme Court has been willing to give for sexual-orientation discrimination. As I've argued before, I think this is a mistake on the part of the opponents of Proposition 8. If they want the analogy with Loving v. Virginia and the overturning of bans on interracial marriage, they ought to be presenting this as a case of sex discrimination, not sexual-orientation discrimination. A black person under Virginia's law could marry a black person but not a white person. A white person could marry a white person but not a black person. So the marriage rights of a black person differed from the marriage rights of a white person in terms of who they could marry. That's race discrimination, which faces a strict scrutiny test, the strongest test the Supreme Court recognizes for discrimination cases.
Similarly, a restriction on marriage to opposite-sex couples does treat one group differently from another group. But those groups are not gays and straights. A straight man can marry the same people as a gay man. The discrimination is along sex lines. A man can't marry the same people as a woman. That's sex discrimination, by the same sort of reasoning that you find in Loving v. Virginia. It's not sexual-orientation discrimination. Sex discrimination faces intermediate scrutiny, the middle-level test of the three the Supreme Court recognizes for discrimination cases. Sexual-orientation faces only rational basis scrutiny, which is the weakest of the tests. So by Supreme Court precedent, the opponents of Proposition 8 would be better suited to pursue their arguments in terms of sex discrimination, which would be both more analogous to Loving v. Virginia and more difficult to get a law past it because of the higher scrutiny. But they continue to push it as a sexual-orientation discrimination claim, which I think helps their purposes much less.
2. The basic claim of the opinion is that there is no rational basis for a law like this, a claim that I think is obviously false. To pass rational basis scrutiny, all there needs to be is some sort of reason-based argument for the law or provision in question, not one that the Court even needs to think is a very good argument, just one that a rational person could support with some reasoning. It has to be a pretty grossly-awful argument to fail rational basis review. The Supreme Court has consistently upheld that stupid laws can pass rational basis review. The Ninth Circuit's opinion in this case says exactly that. Proposition 8 fails rational basis review because it doesn't even have a stupid but somewhat rational connection between the law and some hypothetical government interest. And the key point they were addressing was not same-sex marriage bans in general but just ones in states where there are already civil unions. The decision is silent on whether there's a rational basis for same-sex marriage bans themselves. Their argument is that there's nothing to a same-sex marriage ban when all the rights of marriage are already present. It's a symbolic law, and there's no rational basis for symbolic laws.
Basically what they're saying is that there's no even minimally-rational basis for reserving the word 'marriage' for opposite-sex couples while observing civil unions for the issues of rights. But I can think of several, and even if they're not very good arguments they might pass the rational-basis test as long as they're not such awful arguments that the reasoning is utterly unconnected with the law itself. Here are a few. Some people want to keep government out of marriage. Passing civil-union laws is fine, according to this view, but having the government recognize more marriages rather than fewer marriages is the wrong direction. I have a lot of sympathy for this view, and the reasoning strikes me as certainly passing rational-basis review.
Another basis is preferring an honorific title for traditional marriage because of its historic role and greater natural connection with childrearing. This is not a non-sequitur, since there is a greater connection between traditional marriage and childrearing than there is with same-sex marriage, and it doesn't have to pass the test of rigorous and careful argumentation to be a rational basis. The mere historical connection makes it not completely arbitrary, and that's enough to pass rational-basis review. So one could favor civil unions for actual rights while wanting to reserve the word 'marriage' for something that recognizes the traditional institution for its contribution to childrearing that the new-fangled same-sex marriage concept is not able to convey, and this is so even if it's not a very good ethical argument to reserve that word for traditional marriage. All that there needs to be is some non-arbitrary connection, and there's at least that.
A third argument I've heard sometimes is that same-sex marriage encourages legitimizing sexual relationships that are much more prone to divorce or breakup than opposite-sex marriages, and that result would undermine marriage as an institution. Again, this doesn't have to be a very good argument. It might well be a terrible argument. It might be that affirming same-sex relationships as marriages would actually have the opposite effect. But all that matters for rational-basis review is that a legitimate argument can be put forward that isn't completely unrelated to the state interest in question, and that condition seems to be met. You'd need to do some empirical study to show whether this is a good argument, but on the face of it it's not so stupid that it's irrelevant to the issue at stake. Some reasoning is put forward, and it's reasoning that has to be evaluated, reasoning that's not so obviously bad that you can dismiss it out of hand, and that's the test that the Ninth Circuit claims to be using.
As I've said, I don't think it's in the best interest of opponents of Proposition 8 to use rational-basis review when they can use intermediate scrutiny for sex-discrimination. Intermediate scrutiny requires that the basis being presented is substantially related to the legitimate government purpose, and I'm not sure all the above arguments would pass that. The third almost certainly wouldn't, in my view. I think the second might, and I'm not sure you can get out of the first one even with strict scrutiny. But my point is that they'd have an easier time of it if they didn't insist on treating this as sexual-orientation discrimination, which isn't the most accurate way to go anyway if they want to propose a parallel with Loving v. Virginia. I suspect it will all come down to Justice Anthony Kennedy anyway, though, and he's already on record saying that he thinks same-sex marriage is not required by previous Supreme Court decisions, so he'd have to think there's some new argument here that changes everything he's already written.