Former President Bill Clinton says the U.S. Supreme Court should overturn the Defense of Marriage Act, the measure he signed into law in 1996.
DOMA defines marriage as being between one man and one woman. That means a state where same-sex marriage is illegal doesn't have to recognize same-sex marriage from another state.
It also means same-sex couples don't receive federal benefits.
Clinton said he now believes that the law is unconstitutional.
"When I signed the bill, I included a statement with the admonition that 'enactment of this legislation should not, despite the fierce and at times divisive rhetoric surrounding it, be understood to provide an excuse for discrimination,'" Clinton said.
"Reading those words today, I know now that, even worse than providing an excuse for discrimination, the law is itself discriminatory," he added. "It should be overturned."
A decision from the Supreme Court is expected in June.