BOSTON (AP) — A battle over a law that denies federal benefits for married same-sex couples is headed to an appeals court in Massachusetts, the first state in the nation to legalize gay marriage.

The federal Defense of Marriage Act defines marriage as a union between a man and a woman.

In 2010, a federal judge in Massachusetts declared a key section of the law unconstitutional after the state attorney general and a gay rights legal group sued. The judge found that the law is unconstitutional because it interferes with the right of a state to define marriage and denies married gay couples an array of federal benefits given to heterosexual couples.

An appeal by a bipartisan congressional group will be heard Wednesday by the federal appeals court in Boston.

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