United States v. Windsor is an appellate case pending in the United States Supreme Court of a lawsuit in which the United States Court of Appeals for the Second Circuit affirmed the U.S. District Court for the Southern District of New York's decision in Windsor v. United States, which found Section 3 of the Defense of Marriage Act (DOMA) unconstitutional, as it defines the term marriage as "a legal union between one man and one woman as husband and wife" and spouse as "a person of the opposite sex who is a husband or a wife".