A case trying to strike down the Defense of Marriage Act (1996) began Thursday at a federal courthouse in Massachusetts.

The Defense of Marriage Act or DOMA defines the federal definition for marriage between a man and a woman. The act effectively allows states not to recognize same-sex marriages performed in other states and excludes same-sex married couples from federal benefits offered to heterosexual married couples.

Although President Barack Obama said he is committed to repeal DOMA someday, the US Justice Department is tasked with defending the law’s constitutionality, said Justice Department attorney W. Scott Simpson.

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