BOSTON, (Reuters) – In a victory for gay rights in  the United States, a U.S. district court judge in Massachusetts  ruled yesterday that a federal ban on same-sex marriage is  unconstitutional.

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, arguing that the law interferes  with the right of states to define marriage.

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. “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.