How did District of Columbia v. Heller change the interpretation of the Second Amendment?

In the landmark 2008 case District of Columbia v. Heller, the U.S. Supreme Court fundamentally shifted the interpretation of the Second Amendment by endorsing the "individual-right" theory.1

Writing for the majority, Justice Antonin Scalia argued that the amendment protects an individual's right to possess firearms for traditionally lawful purposes, such as self-defense within the home, independent of any service in a militia. This ruling explicitly rejected the "collective-right" theory, which had previously suggested the amendment only protected the right to keep and bear arms in connection with state-regulated militia service.1

The Court concluded that the amendment's operative clause—"the right of the people to keep and bear Arms, shall not be infringed"—codifies a right rooted in English common law. By identifying self-defense as the "central component" of this right, the decision established a new constitutional standard that limited the government's ability to prohibit handgun possession for law-abiding citizens.1