A federal appeals court in New York on Thursday became the nation's second to deem the Defense of Marriage Act unconstitutional.
The divisive Clinton-era law was passed in 1996 and bars federal recognition of same-sex marriages and says states cannot be forced to recognize such marriages from other states.
The court determined that the federal law violates the Constitution's equal protection clause. A federal appeals court in Boston made a similar ruling in May, but the moves are considered largely symbolic as the issue is expected to be eventually decided by the U.S. Supreme Court.
In February, the Obama administration ordered the Justice Department to stop defending the constitutionality of the law.
Currently, Massachusetts, Connecticut, Iowa, Vermont, New Hampshire, New York and the District of Columbia issue marriage licenses to same-sex couples.
Maryland, Washington, Maine and Minnesota are voting on the issue in November referendums.
Five states -- Delaware, Hawaii, Illinois, New Jersey and Rhode Island -- currently allow civil unions that provide rights similar to marriage.