For nearly 70 years after United States v. Miller (1939), legal scholars fought over whether the Second Amendment protected each person's right to own a gun or only a state's right to arm its militia. The Supreme Court settled the question on June 26, 2008, in District of Columbia v. Heller. Justice Antonin Scalia, writing for a 5-4 majority, struck down Washington, D.C.'s handgun ban and ruled that the Second Amendment guarantees an individual right to keep and bear arms for self-defense in the home, unconnected to militia service. The decision invalidated D.C.'s requirement that lawfully owned firearms be kept disassembled or trigger-locked, calling it an unconstitutional barrier to the "core lawful purpose of self-defense." Heller did not end the gun debate -- the Court said the right is not unlimited and that regulations on felons, the mentally ill, and sensitive places remain "presumptively lawful" -- but it permanently shifted the legal ground. Every major gun case since, including McDonald v. Chicago (2010) and New York State Rifle v. Bruen (2022), builds on Heller's individual-right framework.