Ex parte Quirin is a landmark U.S. Supreme Court case from 1942 that addressed the legality of military tribunals for enemy combatants captured during wartime. The decision affirmed the government's authority to try enemy combatants by military commission rather than civilian courts, highlighting the balance between national security and individual rights during times of war. The case involved a group of German saboteurs who were captured in the U.S. and subsequently tried by a military tribunal, raising significant questions about due process and the definition of lawful combatants.