WASHINGTON - The Supreme Court turned to same-sex marriage Friday in a big way, by agreeing to review a California ballot measure that banned it and a federal law that blocks benefits for married same-sex couples.

In an ambitious move, the justices agreed to second-guess a lower court's decision striking down California's Proposition 8. Simultaneously, they agreed to consider challenges to the federal Defense of Marriage Act, which blocks same-sex married couples from receiving a host of federal benefits.

The separate cases, to be heard next year, will thrust the often-divided high court into hot political territory and tricky constitutional terrain.

It "tees up the fundamental question of whether the Constitution's promise of equality for all persons applies to gay men and lesbians when it comes to marriage," declared David Gans, the civil rights director of the Constitutional Accountability Center, which supports same-sex marriage.

Meeting in a private session Friday morning, justices had to pick and choose among 10 different appeals that deal in some fashion with same-sex marriage. Eight of the appeals cases challenged the federal Defense of Marriage Act. One appeal involved an Arizona law on benefits for state workers, and one dealt with California's Proposition 8.

The justices' action came a day after Maryland issued its first same-sex marriage licenses, after voters approved a ballot measure last month.

Advocates from both sides voiced confidence Friday that they will prevail once the court hears arguments, which could happen in March.

California Attorney General Kamala Harris, an opponent of Proposition 8, said the court's decision to hear the case "takes our nation one step closer to realizing the American ideal of equal protection under the law for all people," while National Organization for Marriage chairman John Eastman called the decision "a strong signal" that the Supreme Court will reverse the lower courts and uphold Proposition 8.

At a dance club near California's state Capitol, a handful of same-sex marriage advocates, hoping the court would decline to hear the case, had waited for hours for the decision Friday and were crestfallen when it came. Ken Pierce, a spokesman for the Sacramento advocacy group Equality Action Now, lamented that "we've waited so long" for same-sex marriage to be upheld.

As is customary, the justices didn't explain their decision about which cases to hear. No decision was announced on the Arizona case.

The California state ballot measure declared that "only marriage between a man and a woman is valid or recognized." The state's voters approved it in 2008, casting into limbo the status of same-sex couples who had already been married in the state. More than 18,000 same-sex marriage licenses were issued in California before the ballot measure passed.

In a narrowly written decision issued in February, the U.S. Court of Appeals for the Ninth Circuit struck down Proposition 8 on the basis that it stripped individuals of rights that had been granted when same-sex marriages were allowed.

The Supreme Court could issue either a broad or a narrow ruling eventually. Justices might decide that the Constitution protects same-sex marriage rights in all states, or just in California, or they might uphold Proposition 8. Justices also left themselves a possible escape route, if they decide that the individuals who support Proposition 8 might lack the legal standing to sue.

The appellate court decision striking down the California ballot measure didn't present a conflict with decisions in other appellate circuits, which is often a criterion for the Supreme Court deciding to hear a case. Although nine states and the District of Columbia now authorize gay marriage, no other state has put itself in California's position of first granting and then revoking a right to same-sex marriage.

By contrast, the Defense of Marriage Act cases that the Supreme Court will hear involved appellate courts striking down a federal law, which is something the high court usually wants to review.

Congress passed the Defense of Marriage Act, signed by then-President Bill Clinton in 1996, by wide margins after occasionally heated debate. The bill's author in the House of Representatives, then-Rep. Bob Barr, a Georgia Republican, said the measure would protect against "homosexual extremists" whose beliefs embodied "the flames of hedonism, the flames of narcissism, the flames of self-centered morality."

Attorneys defending the Defense of Marriage Act now prefer less impassioned rhetoric.

The law "does not bar or invalidate any state-law marriage," attorney Paul Clement wrote in a brief, adding that the measure "simply asserts the federal government's right as a separate sovereign to provide its own definition for purposes of federal programs and funding."