Judge rules gay marriage ban unconstitutional

Supporters of gay marriage rally outside the federal courthouse in San Francisco, California January 11, 2010.

BOSTON (Reuters) - A U.S. district court judge in Massachusetts ruled on Thursday a federal ban on same-sex marriage is unconstitutional because it interferes with the right of states to define marriage.

Judge Joseph Tauro in Boston ruled in favor of gay couples' rights in two separate challenges to the 1996 Defense of Marriage Act, known as DOMA.

Massachusetts had argued DOMA denied benefits to same-sex couples in the state, where such unions have been legal since 2004. Four other states -- Vermont, New Hampshire, Connecticut and Iowa -- also allow same-sex marriage, as does Washington, D.C.

Tauro agreed with the state's argument and said DOMA forces Massachusetts to discriminate against its own citizens.

"The federal government, by enacting and enforcing DOMA, plainly encroaches upon the firmly entrenched province of the state, and in doing so, offends the Tenth Amendment," Tauro said in his ruling. "For that reason, the statute is invalid."

The Tenth Amendment of the U.S. Constitution says: "The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people."

The Justice Department argued the federal government can determine eligibility requirements for federal benefits, including requiring that those benefits go only to couples in marriages between a man and a woman.

(Reporting by Ros Krasny; Editing by John O'Callaghan)