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The Supreme Court today, in a somewhat surprising decision, took not one but two cases having to do with the fight over marriage equality. This is a very big deal, and not just because it may well mean the end of key provisions of the Defense of Marriage Act.

The outcome could set the overall Constitutional boundaries on gay marriage for a generation or more. 

The first one, which had been expected, is a challenge to the Defense of Marriage Act — the federal law which prevents, for example, legally married same-sex couples in states such as New York and Iowa from getting the same federal benefits that heterosexual married couples receive. As E.J. Graff has described it, the issue there is: “Does the federal government have the right to pick and choose which state marriages it will recognize, or is that unconstitutional, violating the U.S. Constitution’s promise that each American will be protected equally by the law?” Marriage equality advocates believe they have a pretty good chance of winning.

The second case is a bit of a surprise. The Court accepted the California case about Proposition 8 (which defines marriage as between a man and a woman). Here the issue will be more basic: does the Equal Protection clause mean that if state governments recognize any marriages, they must recognize all same-sex marriages? Marriage equality advocates are less confident on this one. But it’s certainly possible that the Supremes could rule narrowly, finding some reason to cover only the California law with their ruling instead of deciding something that would either invalidate all state bans — or establish a strong precedent that states can do what they wish in this area.

Even if the outcome doesn’t resolve all underlying issues, it will almost certainly decide what course this continuing fight will take in the near future. Will marriage continue to mainly proceed in state-by-state battles, or will it (also?) move to Congress as a federal issue? If the court strikes down DOMA, but narrowly, Republicans could try to pass a new version. If it doesn’t strike down DOMA, Dems will likely try to repeal it. And if the decision winds up promising future court fights, then gay and lesbian issues may move to higher importance in battles over the next set of judicial nominations. At the very least the Court will probably determine the nature of this ongoing battle going forward.