Why did Justice John Paul Stevens disagree with the majority in District of Columbia v. Heller?

In District of Columbia v. Heller (2008), Justice John Paul Stevens dissented from the majority’s decision to establish an individual right to possess firearms independent of militia service.1

Stevens argued that the majority failed to provide new evidence demonstrating that the Second Amendment was intended to restrict Congress's authority to regulate civilian firearm use. His primary points of disagreement included:1

• The Preamble: He criticized the majority for "denigrating" the importance of the amendment's preamble ("A well regulated Militia, being necessary to the security of a free State"), arguing that it serves to disambiguate the operative clause rather than being merely prefatory.1
• Legal Precedent: He asserted that the majority misinterpreted the court's previous ruling in United States v. Miller (1939).1
• Historical Consensus: He noted that the majority ignored the collective-right interpretation of the Second Amendment that had been consistently upheld by "hundreds of judges" in the decades following Miller.1

By rejecting the collective-right theory, Stevens maintained that the amendment was historically understood to protect the right to keep and bear arms specifically in connection with service in a militia.1