Updated

The Supreme Court on Wednesday is poised to hand down major rulings on two gay marriage cases that have the potential to reshape the legal landscape for same-sex couples across the country.

One is a challenge to California's voter-enacted ban on same-sex marriage. The other is a challenge to a provision of federal law that prevents legally married gay couples from receiving a range of tax, health and pension benefits.

Court watchers and legal experts are anticipating one of several possible outcomes in the case challenging the constitutionality of California's Proposition 8, which amended the state constitution to define marriage as the union of a man and woman.

One outcome could make bans on gay marriage unconstitutional nationwide; another would legalize gay marriage only in California and six other states that already provide the legal rights of marriage through civil unions or domestic partnerships; three other scenarios would allow same-sex marriages to resume in California itself. The justices also could uphold Prop 8.

The court's justices heard oral arguments in the 4-year-old case in March. Several justices, including some liberals who seemed open to gay marriage, raised doubts at the time that the case was properly before them. Justice Anthony Kennedy, the potentially decisive vote on a closely divided court, suggested that the court could dismiss the case with no ruling at all.

Such an outcome would almost certainly allow gay marriages to resume in California but would have no impact elsewhere.

The justices also have a range of options from which to choose in considering the constitutionality of the federal Defense of Marriage Act provision that defines marriage as between a man and a woman.

The law, known by the shorthand DOMA, affects a range of benefits available to married couples, including tax breaks, survivor benefits and health insurance for spouses of federal employees. The Obama administration abandoned its defense of the law in 2011 but continues to enforce it.

The justices chose for their review the case of Edith Windsor, 83, of New York, who sued to challenge a $363,000 federal estate tax bill after her partner of 44 years died in 2009.

At Kennedy said during a hearing in March that the law appears to intrude on the power of states that have chosen to recognize same-sex marriages. Other justices said the law creates what Justice Ruth Bader Ginsburg called two classes of marriage, full marriage and "skim-milk marriage."

Like the Prop 8 case from California, Windsor's lawsuit could falter on a legal technicality without a definitive ruling from the high court.

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.

In a landmark ruling on Tuesday, the justices voted 5-4 to strip the government of the requirement in the Voting Rights Act that all or parts of 15 states with a history of discrimination in voting, mainly in the South, get Washington's approval before changing the way they hold elections.

The court ruled that the formula determining which states are affected was unconstitutional.
In doing so, the court potentially opened the door for certain states to proceed with voter ID laws and other efforts that to date had been held up because of the Voting Rights Act. Prominent among those are voter identification laws in Alabama and Mississippi.

Texas Attorney General Greg Abbott, a Republican, said his state's voter ID law, which a panel of federal judges blocked as discriminatory, also would be allowed to take effect following Tuesday's ruling.

Attorney General Eric Holder warned states against going too far. He said the Justice Department would not hesitate to take "swift" action against states looking to "take advantage" of the ruling.

He, like President Obama, said he was "deeply disappointed" in the decision, saying discriminatory practices live on and need to be addressed.

The high court is in the midst of a broad re-examination of the ongoing necessity of laws and programs aimed at giving racial minorities access to major areas of American life from which they once were excluded. The justices issued a modest ruling Monday that preserved affirmative action in higher education and will take on cases dealing with anti-discrimination sections of a federal housing law and another affirmative action case from Michigan next term.

The Associated Press contributed to this report.