Second Amendment to the United States Constitution
In 1939, the U.S. Supreme Court made a landmark decision in United States v. Miller (307 U.S. 174 (1939)). The Court determined that Congress could keep people from having certain weapons (in this case, a sawed-off shotgun) because the shotgun would not help maintain a well regulated militia. The Court said the Second Amendment's purpose was to ensure the effectiveness of the military.