The US Supreme Court tackled same-sex unions for a second day Wednesday, indicating it might throw out a federal law that defines marriage in strictly one-man, one-woman terms. For nearly two hours, its nine justices questioned the constitutionality of the Defense of Marriage Act (DOMA), with five of them appearing to lean in favor of striking it down. The controversial 1996 law prevents couples who have tied the knot in nine states -- where same-sex marriage is legal -- from enjoying the same federal rights and benefits as heterosexual couples.

The rights of married same-sex couples will come under scrutiny at the US Supreme Court on Wednesday in the second of two landmark cases being considered by the top judicial panel. After the nine justices mulled arguments on a California law that outlawed gay marriage on Tuesday, they will take up a challenge to the legality of the Defense of Marriage Act (DOMA). The 1996 law prevents couples who have tied the knot in nine states -- where same-sex marriage is legal -- from enjoying the same federal rights as heterosexual couples.

Same-sex marriage takes center stage Tuesday as the US Supreme Court starts hearing oral arguments on the divisive issue in a landmark case. Over two days, lawyers from both sides of the emotionally-charged debate will present their positions before the nine justices as supporters and opponents converge on Washington to rally for their respective positions. The top court will first hear arguments over Proposition 8, a California referendum measure that struck down that state's same-sex marriage initiative in 2008.

Next week, the US Supreme Court will take up the issue of gay marriage, which is legal in nine states and the capital Washington but banned under the federal Defense of Marriage Act of 1996. Here is a rundown of the current statutes governing same-sex unions in the United States, where recent polls show public opinion has swung toward favoring the legalization of gay marriage. FEDERAL BAN DOMA defines marriage as the union of one man and one woman, granting legal recognition only to heterosexual marriages.