The Defense of Marriage Act (DOMA) is a United States federal law passed by the 104th United States Congress and signed into law by President Bill Clinton. It defines marriage for federal purposes as the union of one man and one woman, and allows states to refuse to recognize same-sex marriages granted under the laws of other states. All of the act's provisions, except those relating to its short title, were ruled unconstitutional or legally devoid by Supreme Court decisions in the cases of United States v. Windsor (2013) and Obergefell v. Hodges (2015), which invalidated the law and any enforcement it had.

Same-sex marriage emerged as an issue in the late 1980s, drawing opposition especially from socially conservative groups. Congressman Bob Barr and Senator Don Nickles, both members of the Republican Party, introduced the bill that became DOMA in May 1996. It passed both houses of Congress by large, veto-proof majorities, with opposition coming from approximately one-third of the Democratic caucus in both the House of Representatives and the Senate. Clinton criticized the law as "divisive and unnecessary", but nonetheless signed it into law in September 1996.

Section 2 of the act allows states to deny recognition of same-sex marriages conducted by other states. Section 3 codifies non-recognition of same-sex marriages for all federal purposes, including insurance benefits for government employees, social security survivors' benefits, immigration, bankruptcy, and the filing of joint tax returns. It also excludes same-sex spouses from the scope of laws protecting families of federal officers, laws evaluating financial aid eligibility, and federal ethics laws applicable to opposite-sex spouses.:2324After its passage, DOMA was subject to numerous lawsuits and repeal efforts. In United States v. Windsor (2013), the U.S. Supreme Court declared Section 3 of DOMA unconstitutional under the Due Process Clause, thereby requiring the federal government to recognize same-sex marriages conducted by the states. In Obergefell v. Hodges (2015), the Court held that same-sex marriage was a fundamental right protected by both the Due Process Clause and the Equal Protection Clause. The ruling requires all states to perform and recognize the marriages of same-sex couples, leaving Section 2 of DOMA as superseded and unenforceable.

The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate and largely discretionary appellate jurisdiction over all federal and state court cases that involve a point of federal law, and original jurisdiction over a narrow range of cases, specifically "all Cases affecting Ambassadors, other public Ministers and Consuls, and those in which a State shall be Party." The Court holds the power of judicial review, the ability to invalidate a statute for violating a provision of the Constitution. It is also able to strike down presidential directives for violating either the Constitution or statutory law. However, it may act only within the context of a case in an area of law over which it has jurisdiction. The Court may decide cases having political overtones but has ruled that it does not have power to decide non-justiciable political questions.

Established by Article Three of the United States Constitution, the composition and procedures of the Supreme Court were initially established by the 1st Congress through the Judiciary Act of 1789. As later set by the Judiciary Act of 1869, the Court consists of the chief justice of the United States and eight associate justices. Each justice has lifetime tenure, meaning they remain on the Court until they die, retire, resign, or are removed from office. When a vacancy occurs, the president, with the advice and consent of the Senate, appoints a new justice. Each justice has a single vote in deciding the cases argued before the Court. When in majority, the chief justice decides who writes the opinion of the court; otherwise, the most senior justice in the majority assigns the task of writing the opinion.

The Court meets in the Supreme Court Building in Washington, D.C. Its law enforcement arm is the Supreme Court Police.