Modern Second Amendment doctrine cannot be understood without three Supreme Court decisions: District of Columbia v. Heller, McDonald v. City of Chicago, and Caetano v. Massachusetts. Each addressed a different constitutional question, and together they helped define the scope of the right before later cases further developed the Court’s methodology.
Heller: An Individual Right
In Heller, the Supreme Court held that the Second Amendment protects an individual right to possess a firearm unconnected with service in a militia, particularly for traditionally lawful purposes such as self-defense in the home. The decision invalidated key features of the District of Columbia’s handgun restrictions while also emphasizing that the right is not unlimited.
McDonald: Application to State and Local Government
Heller involved federal authority in the District of Columbia. McDonald addressed whether the protected right also constrains state and local governments. The Court concluded that the Second Amendment right recognized in Heller applies to the states through the Fourteenth Amendment.
Caetano: Modern Arms Are Not Automatically Excluded
Caetano involved a Massachusetts stun-gun prohibition. In a brief per curiam decision, the Court rejected reasoning that a weapon falls outside the Second Amendment merely because it was not in common use when the Amendment was adopted. The decision reinforced the principle that constitutional protection is not frozen to eighteenth-century technology.
What the Three Cases Establish
- The Second Amendment protects an individual right.
- That right applies against state and local governments as well as the federal government.
- The constitutional inquiry is not limited to weapons that existed at the founding.
- The right remains subject to legal limits, and later cases address how those limits are evaluated.
Later Development
Subsequent Supreme Court decisions, including New York State Rifle & Pistol Association v. Bruen and United States v. Rahimi, further developed the framework for assessing firearm regulations. Those later cases do not erase the importance of Heller, McDonald, and Caetano; they build on the constitutional foundation those decisions established.
The three cases are therefore best read as a progression: recognition of the right, incorporation of the right, and clarification that the right cannot be dismissed simply because technology changes.