A U.S. district court judge in Boston has struck down the 1996 federal ban on gay marriage, saying it is unconstitutional because it violates a state's right to define marriage.

Judge Joseph Tauro ruled in two separate challenges to the Defense of Marriage Act. Massachusetts had argued that the law denied Medicaid and other federal benefits to gay married couples in the state, which legalized same-sex unions in 2004.

The Justice Department argued the federal government can establish eligibility requirements for federal benefits, even those bestowed only on heterosexual couples.

For purposes of federal law, the act defines marriage as a legal union between a man and a woman.

(Posted by Michael Winter)