The Supreme Court is hearing the second of back-to-back gay marriage cases, a constitutional challenge to the law that prevents legally married gay Americans from collecting federal benefits generally available to straight married couples.
A section of the 1996 Defense of Marriage Act says marriage may only be a relationship between a man and a woman for purposes of federal law, regardless of state laws that allow same-sex marriage.
Lower federal courts have struck down the measure. The justices, in scheduled argument Wednesday, will consider whether to follow suit.
The Defense of Marriage Act argument follows Tuesday's case over California's ban on same-sex marriage, a case in which the justices indicated they might avoid a major national ruling on whether America's gays and lesbians have a right to marry.