The U.S. Supreme Court agreed Friday to take its first serious look at the issue of gay marriage, granting review of California's ban on same-sex marriage and of a federal law that defines marriage as only the legal union of a man and a woman.

At the very least, the court will look at this question: When states choose to permit the marriages of same-sex couples, can the federal government refuse to recognize their validity? But by also taking up the California case, the court could get to the more fundamental question of whether the states must permit marriages by gay people in the first place.

The California case involves a challenge to Proposition 8, a constitutional amendment approved by 52 percent of voters in 2008. It banned same-sex marriages in the state and went into effect after 18,000 couples were legally married earlier that year.

A federal judge declared the ban unconstitutional, and a federal appeals court upheld that ruling, though on narrower grounds that apply only to California. Now that the Supreme Court is wading into the battle, the justices could decide the more basic issue of whether any state can ban same-sex marriage under the Constitution's guarantee of equal protection of the law. Or they could limit their ruling to apply only to the ban in California.

The Supreme Court also agreed Friday to hear a challenge to the federal Defense of Marriage Act, known as DOMA, passed by overwhelming margins in both houses of Congress in 1996 and signed by President Clinton. A provision of the law specifies that, for federal purposes, "the word 'marriage' means only a legal union between one man and one woman as husband and wife."
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Because of DOMA, gay couples who wed in the nine states where same-sex marriage is permitted are considered legally married only under state law. The federal government is barred from recognizing their marriages. As a result, they are denied over 1,000 federal benefits that are available to traditional couples.

After first supporting DOMA in court, the Obama administration concluded last year that it violated the Constitution's guarantee of equal protection under the law.

"We cannot defend the federal government poking its nose into what states are doing and putting the thumb on the scale against same-sex couples," President Obama said in explaining the change.

Gay married couples in five states filed lawsuits challenging DOMA as an unconstitutional denial of their right to equal protection. After the Obama Justice Department declined to defend the law, House Republicans stepped in to carry on the legal fight.
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A Supreme Court decision striking down the Defense of Marriage Act would not, by itself, require states to allow same-sex marriages. But the federal government would be required to recognize those marriages in the states where they are legal.

The cases will be argued before the justices in March, with a decision expected by late June.