In addition, the same-sex marriage advocates have won the vast majority of lower court cases on the issue since Windsor. The Sixth Circuit decision that the Supreme Court decided to review today is the only one of five court of appeals decisions won by the anti-gay marriage side over the last two years (I criticized the Sixth Circuit ruling, written by prominent conservative Judge Jeffrey Sutton, in this post). Thanks to a combination of judicial decisions and legislative changes, there are now 36 states that recognize same-sex marriage. That creates a very different situation than existed even a few years ago, when same-sex marriage was only legal in a small minority of jurisdictions.
Furthermore, both elite and public opinion have moved strongly in a pro-gay marriage direction in recent years. Even some conservative evangelicals have begun to step back from opposing same-sex marriage. The Court certainly does not always follow public opinion. But if a majority of justices are inclined to endorse a constitutional right to same-sex marriage, they are now unlikely to be deterred from doing so by fear of a massive political backlash, of the sort that would have greeted such a ruling a decade ago.
I don’t claim that any of these external factors by themselves prove that the Court should strike down laws banning same-sex marriage. Rather, in my view, they simply make it more feasible for the Court to recognize the validity of arguments against these laws that should have been compelling all along, but had little chance of getting serious consideration in an atmosphere where majority opinion was deeply hostile to gay marriage, and even gays and lesbians more generally. Some of those arguments are based on originalist, as well as living constitutionalist reasoning.
If the Court does issue a decision striking down laws banning same-sex marriage, there are several possible rationales it could adopt to justify that outcome, and the choice between them is likely to have important implications for future cases. In my view, the best option is for the Court to rule that laws banning same-sex marriage are unconstitutional because they discriminate on the basis of sex. If the pro-gay marriage side does prevail, it will be interesting to see which of the various arguments for that result gains traction with the justices.
UPDATE: I should note that, in principle, the Supreme Court need not choose just one rationale for striking down laws banning same-sex marriage. It could instead embrace two or more of them. That, too, of course, would be an important step and might have even broader precedential impact than endorsing just one rationale would.
UPDATE #2: It may be worth noting that the Sixth Circuit decision the Supreme Court has decided to review is actually a consolidation of four different cases, including some that challenge the constitutionality of state laws banning same-sex marriage, and others that challenge states’ refusal to recognize same-sex marriages contracted in other states.