The Second Amendment (Amendment II) 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 United States Bill of Rights. In District of Columbia v. Heller (2008), the Supreme Court affirmed that the right belongs to individuals, for self-defense in the home, while also including, as dicta, that the right is not unlimited and does not preclude the existence of certain long-standing prohibitions such as those forbidding "the possession of firearms by felons and the mentally ill" or restrictions on "the carrying of dangerous and unusual weapons". In McDonald v. City of Chicago (2010) the Supreme Court ruled that state and local governments are limited to the same extent as the federal government from infringing upon this right. New York State Rifle & Pistol Association, Inc. v. Bruen (2022) assured the right to carry weapons in public spaces with reasonable exceptions.
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 1689. Sir William Blackstone described this right as an auxiliary right, supporting the natural rights of self-defense and resistance to oppression, and the civic duty to act in concert in defense of the state. While both James Monroe and John Adams supported the Constitution being ratified, its most influential framer was James Madison. In Federalist No. 46, Madison wrote how a federal army could be kept in check by the militia, "a standing army ... would be opposed [by] militia." He argued that State governments "would be able to repel the danger" of a federal army, "It may well be doubted, whether a militia thus circumstanced could ever be conquered by such a proportion of regular troops." He contrasted the federal government of the United States to the European kingdoms, which he described as "afraid to trust the people with arms", and assured that "the existence of subordinate governments ... forms a barrier against the enterprises of ambition".