It’s no shocker that the Supreme Court of the United States decided this afternoon to hear United States v. Windsor, which calls into question the constitutionality of Section 3 of the Defense of Marriage Act. By defining the word “marriage” to apply solely to “a legal union between one man and one woman as husband and wife,” this provision excludes legally married same-sex couples from every single one of the 1,138 federal benefits and protections available to all legally married heterosexual couples. It also marks the only time in our nation’s entire history that the federal government has not deferred to a state’s definition of who is and is not married.   And make no mistake: the 1,138 federal benefits and protections that Congress denied to legally married same-sex couples are B-I-G benefits: think Social Security and pension benefits; health insurance free of the “gay tax” that applies to “unmarried” couples (because health insurance is subsidized by the federal government); the Family Medical Leave Act; the ability to sponsor a non-resident spouse for immigration purposes; and estate/death protections that allow a spouse to leave assets to their other spouse (including the family home) without incurring a tax penalty.

It’s this last question in particular that comes to the fore in the Windsor case, which concerns Edith Windsor and Thea Clara Spyer, who were legally married in Canada in 2007 and resided in New York (the only state to recognize same-sex marriages legally performed elsewhere until the state legislature’s decision, in the summer of 2011, to stop impeding marriage equality within its own borders). When Spyer died in 2009, leaving her property to her spouse, DOMA prevented Windsor from being treated as a legally married surviving spouse, resulting in a tax bill of $360,000 that no opposite-sex spouse would ever be required to pay. A federal appeals court found Section 3 unconstitutional, and ruled in Windsor’s favor.

Far more surprising is the Court’s decision to hear Hollingsworth v. Perry from California, better known as the Prop 8 case. Writing for the Ninth Circuit 2-1 majority last February, Justice Reinhardt wrote a very narrow, California-centric decision that found that Prop 8’s amendment of California’s state constitution failed the rational basis test and violated the Equal Protection Clause of the Fourteenth Amendment of the United States. Reinhardt’s decision in no way took up the question of whether lesbian and gay Americans have a fundamental right to marriage—but the Supreme Court, theoretically, could.

But here’s the real kicker about both of these cases. The first question SCOTUS will take up this spring will be questions about standing—in essence, the legal right to appeal. The question in Hollingsworth, where the government of California decided against continuing to defend Prop 8 after its initial defeat before Justice Walker in district court, will be whether Prop 8’s supporters had standing to bring the case before the Ninth Circuit to begin with, once the state decided that it would no longer defend it. If SCOTUS says no, Walker’s earlier decision would stand and same-sex marriage would go forward in California. A similar question comes up in Windsor, since the Obama administration stopped defending DOMA in the courts last year. That’s how we wound up with the alleged House Republican-controlled Bipartisan Legal Advisory Group (BLAG) appealing the case. If SCOTUS decides that BLAG has no real standing to do so, the decisions of the two earlier federal appeals courts will go forward. That would leave the issue of the constitutionality of DOMA to each of the federal circuits, a process that could result in conflicting rulings.

Needless to say, the advocates bringing these cases sound exultant today. James Esseks, director of the ACLU lesbian gay bisexual and transgender project, blogged “The Windsor and Perry rulings, expected in June 2013, will be a watershed moment if our side wins either one.”

Given the excellent chance that the current SCOTUS, which tends to steer clear of making broad decisions, punts, the last, best word on what’s happening now may come from Dale Carpenter, law professor at University of Minnesota. “I’m generally skeptical that there are five Justices willing to vote for marriage equality,” Carpenter told me. “But in both of these cases the court has given itself a potential way to avoid decisions on the merits. So we have the potential here for results that guarantee marriage equality without requiring the justices to explain why.”

Fascinating stuff. Stay tuned.