A New York federal appeals court heard arguments Thursday on a case challenging the Defense of Marriage Act (DOMA).
The three judge panel will decide whether the federal law protecting traditional marriage is constitutional.
An 83-year-old lesbian filed the lawsuit, claiming because DOMA bans national recognition of her same-sex marriage, she was not entitled to an inheritance after her spouse died and had to pay hundreds of thousands of dollars in estate taxes.
DOMA does not federally recognize same-sex unions and was enacted by President Bill Clinton in 1996.
Critics argue that the law intrudes upon state's rights to regulate domestic policy.
Last year, President Barack Obama and Attorney General Eric Holder made headlines when they told the Department of Justice to no longer defend the law.
A ruling is not expected for months.