Same-sex couples are most likely to get a positive ruling on DOMA, the so-called Defense of Marriage Act (more accurately: the Denial of Marriage Act.) The outlook here is somewhat positive for one simple reason: this court seems to have a fairly consistent disdain for laws passed by Congress. It invalidated a bipartisan deal on campaign finance in its Citizens United decision, for example, and just today nullified a broadly bipartisan vote in 2006 that reauthorized the Voting Rights Act.
Congress also passed DOMA. In today's decision on voting rights, the majority argued that the situation had changed dramatically since the act's passage several decades ago, and that minorities no longer need the level of protection provided by the Voting Rights Act. Under this reasoning, the court could also determine that the situation has changed dramatically concerning attitudes toward LGBT rights and that, as a result, DOMA was no longer appropriate.
However, if the justices impose this logic, that could pose a problem for opponents of Proposition 8, the ballot initiative that banned same-sex marriage in California after a state court had declared it legal. It could be argued that evolving cultural norms make it unnecessary for the court to intervene, and that this evolution toward the acceptance of same-sex marriage should simply be allowed to run its course. The court tends to trust voters and states a lot more than it does Congress, so it would (in theory) be far less likely to overturn a state-passed initiative than it would a congressional law.
This court has, on balance, favored states' rights over federalism. This would argue for a ruling upholding Prop. 8.
Ironically, the conservative wing that constitutes a slim majority on the court has also argued that it's too soon to weigh in on the issue because same-sex marriage is (supposedly) a relatively new phenomenon. The court tends to take its time on validating cultural change, so it's unlikely to do so in this case before it's ready. One thing worth remembering is that decisions weigh heavily on precedent - not just written legal precedent, but common law and cultural precedent, too. The perceived cultural precedent for limiting marriage to one man and one woman mitigates against any sweeping action on the court's part to sanction same-sex marriage on the basis of equal protection.
It's also possible the court will allow the lower court ruling in Prop. 8 to stand on the grounds that its proponents didn't have proper legal standing to appeal the case after lower courts invalidated California's ban on equal-protection grounds. The state's governor and attorney general (who is now its governor) both declined to appeal the case because they agreed with the lower court's decision overturning the initiative, so a group of citizens took up the appeal. Whether they had a right to do so is an open question, and this court has shown a tendency to use legal technicalities as a means to avoid far-reaching decisions.
Conservative courts tend to view far-reaching decisions, and this court is no exception. The chances for a sweeping decision declaring same-sex marriage legal nationwide on equal protection grounds seem slim to none given the court's propensity for 1) yielding to precedent, whether legal or cultural, 2) favoring states over the federal government and 3) avoiding "big" decisions.
On DOMA, however, the court's tendency to act as a foil for Congress and could swing things the other way. Moreover, a decision striking down DOMA would not be nearly as sweeping. It is clearly important, because it would clear the way for same-sex married couples to access federal benefits, but it would not force states to recognize such marriages or offer state benefits to such couples.
Of course, it probably all comes down to a single "swing" vote: Justice Anthony Kennedy, who more often votes on the conservative side but has favored same-sex rights in the past. Kennedy, however, tends to be cautious, so the guess here is that he'll avoid signing on to any broad equal protection ruling on Prop. 8.
Here are my odds, purely subjective on my part, on the two cases:
- DOMA: 70 percent chance the court will invalidate it, 30 percent that the law will be allowed to stand.
- Prop. 8: 50 percent chance the court will find the challenge lacked standing and allow the lower-court's ruling (against the proposition) to stand; 49 percent chance it will overturn the lower court ruling and uphold Prop. 8 out of "respect" for the state's electorate; <1 percent chance of a sweeping equal protection ruling legalizing same-sex marriage nationwide.
I hope my prediction on Prop. 8 is unduly pessimistic. I hope I'm wrong. Given the court's previous behavior, however, this is my best guess. I'm hoping to wake up tomorrow to a pleasant surprise.