The Second Amendment to the United States Constitution protects the right to keep and bear arms. It was ratified on December 15, 1791, along with nine other articles of the Bill of Rights. The Second Amendment was based partially on the right to keep and bear arms in English common law and was influenced by the English Bill of Rights of 1689. The amendment states: "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed".

The Second Amendment has been the subject of much debate and interpretation. In United States v. Miller (1939), the Supreme Court ruled that the Second Amendment did not protect weapon types not having a "reasonable relationship to the preservation or efficiency of a well regulated militia". However, in District of Columbia v. Heller, the Supreme Court handed down a landmark decision that held the amendment protects an individuals right to keep a gun for self-defense. This was the first time the Court had ruled that the Second Amendment guarantees an individuals right to own a gun.

In summary, the Second Amendment to the United States Constitution protects the right to keep and bear arms, and its interpretation has been the subject of much debate and legal precedent.