On this day in 2013, the Supreme Court heard oral arguments in United States v. Windsor, a landmark case in the evolution of marriage equality rights.

Windsor was a challenge to a provision of the federal Defense of Marriage Act (DOMA) of 1996. The provision at issue stated that under federal law, “marriage” and “spouse” applied only to marriages between a man and a woman. The effect of this provision was to deny same-sex couples federal marriage benefits.

The New York couple at the center of the lawsuit, Edith Windsor and Thea Clara Spyer, wed in Canada in 2007. New York legally recognized their marriage. Spyer died in 2009, leaving her estate to Windsor. But since their marriage was not recognized under federal law, Windsor did not quality for a marital tax exemption and she had to pay $363,000 in federal taxes. Windsor filed suit, arguing that the provision of DOMA limiting marriage to heterosexual couples violated her due process and equal protection rights.

The Supreme Court ruled in Windsor’s favor. In his opinion for the Court, Justice Kennedy noted that DOMA’s provision ran up against federalism principles, “which allow states to largely chart their own course,” as well as equal protection concerns. The issue, he wrote, was one of “basic fairness and human dignity.” The effect of DOMA was to impose a “disadvantage, a separate status, and so a stigma” on same sex couples that denied them equal protection under the law.    

The Court held that same-sex couples are guaranteed federal benefits if they lived in a state that recognized same-sex marriage. The decision did not however, guarantee a federal right to same-sex marriage. This issue would not be decided until two years later, in 2015, when the Court decided Obergefell v. Hodges.