The Supreme Court can choose from a wide array of outcomes in ruling on California's Proposition 8 ban on same-sex marriage and the federal Defense of Marriage Act.
The federal law, known by the shorthand DOMA, defines marriage as the union of a man and a woman and therefore keeps legally married gay Americans from collecting a range of federal benefits that generally are available to married people.
The cases will be argued Tuesday and Wednesday; rulings are not likely before late June.
The justices might come out with rulings that are simple, clear and dramatic. Or they might opt for something narrow and legalistic.
The court could strike down dozens of state laws that limit marriage to heterosexual couples, but it also could uphold gay marriage bans or say nothing meaningful about the issue at all.
A look at potential outcomes for the Proposition 8 case and then for the case about DOMA:
Q. What if the Supreme Court upholds Proposition 8?
A. This would leave gay Californians without the right to marry in the state and would tell the roughly 40 states that do not allow same-sex marriages that there is no constitutional problem in limiting marriage to a man and a woman.
Such an outcome probably would trigger a political campaign in California to repeal Proposition 8 through a ballot measure and could give impetus to similar voter or legislative efforts in other states.
Q. What if the court strikes down Proposition 8?
A. A ruling in favor of the two same-sex couples who sued to invalidate the voter-approved gay marriage ban could produce one of three possibilities. The broadest would apply across the country, in effect invalidating constitutional provisions or statutes against gay marriage everywhere.
Or a majority of the justices could agree on a middle option that applies only to California as well as Colorado, Delaware, Hawaii, Illinois, Nevada, New Jersey, Oregon, and Rhode Island. Those states already treat gay and straight couples the same in almost every respect through civil unions or domestic partnerships. The only difference is that gay couples are not allowed to marry. Gov. John Hickenlooper, D-Colo., signed his state's civil unions law Thursday.
This "nine-state solution" would say that the Constitution forbids states to withhold marriage from same-sex couples while giving them all the basic rights of married people. But this ruling would not implicate marriage bans in other states and would leave open the question of whether states could deprive gay couples of any rights at all.
The narrowest of these potential outcomes would apply to California only. The justices essentially would adopt the rationale of the federal appeals court that found that California could not take away the right to marry that had been granted by the state Supreme Court in 2008 before Proposition 8 passed later that year.
In addition, if the Supreme Court were to rule that gays and lesbians are deserving of special protection from discriminatory laws, it is unlikely that any state ban on same-sex marriage could survive long, even if the justices don't issue an especially broad ruling in this case.
Q. Are there other potential outcomes?
A. Yes, the court has a technical way out of the case without deciding anything about same-sex marriage. The Proposition 8 challengers argue that the private parties defending the provision — members of the group that helped put the ban on the ballot — did not have the right to appeal the trial judge's initial decision striking it down or that of the federal appeals court.
The justices sometimes attach great importance to this concept, known as standing. If they find Proposition 8's proponents lack standing, the justices also would find the Supreme Court has no basis on which to decide the case.
The most likely outcome of such a ruling also would throw out the appeals court decision that struck down the ban but would leave in place the trial court ruling in favor same-sex marriage. At the very least, the two same-sex couples almost certainly would be granted a marriage license, and Gov. Jerry Brown, D-Calif., who opposes Proposition 8, probably would give county clerks the go-ahead to issue marriage licenses to same-sex couples.
Q. Are the possibilities for the DOMA case as complicated?
A. No, although there are some technical issues that could get in the way of a significant ruling.
Q. What happens if the court upholds Section 3 of DOMA, defining marriage for purposes of federal law as the union of a man and a woman?
A. Upholding DOMA would not affect state laws regarding marriage but would keep in place federal statutes and rules that prevent legally married gay Americans from receiving a range of benefits that are otherwise available to married people. These benefits include breaks on estate taxes, health insurance for spouses of federal workers and Social Security survivor benefits.
Q. What if the court strikes down the DOMA provision?
A. A ruling against DOMA would allow legally married gay couples, or in some cases, a surviving spouse in a same-sex marriage, to receive benefits and tax breaks resulting from more than 1,000 federal statutes in which marital status is relevant. For 83-year-old Edith Windsor, a New York widow whose case is before the court, such a ruling would give her a refund of $363,000 in estate taxes that were paid after the death of her spouse, Thea Spyer.
Q. What procedural problems could prevent the court from reaching a decision about DOMA?
A. As in the Proposition 8 case, there are questions about whether the House Republican leadership has the right to bring a court case to defend the law because the Obama administration decided not to.
House Republicans argue that the administration forfeited its right to participate in the case because it changed its position and now argues that the provision is unconstitutional.
If the Supreme Court finds that it does not have the authority to hear the case, Windsor probably would still get her refund because she won in the lower courts, but there would be no definitive decision about the law from the nation's highest court and it would remain on the books.