The Second Amendment to the US Constitution provides: "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms shall not be infringed." Senior Judge Laurence Silberman wrote for the majority:

...the Second Amendment protects an individual right to keep and bear arms. That right existed prior to the formation of the new government under the Constitution and was premised on the private use of arms for activities such as hunting and self-defense, the latter being understood as resistance to either private lawlessness or the depredations of a tyrannical government. In addition, the right to keep and bear arms had the important and salutary civic purpose of helping to preserve the citizen militia. The civic purpose was also a political expedient for the Federalists in the First Congress as it served, in part, to placate their Antifederalist opponents. The individual right facilitated militia service by ensuring that citizens would not be barred from keeping the arms they would need when called forth for militia duty. Despite the importance of the Second Amendment’s civic purpose, however, the activities it protects are not limited to militia service, nor is an individual’s enjoyment of the right contingent upon his or her continued or intermittent enrollment in the militia.

In dissent Judge Karen Henderson, a Reagan appointee, countered that the Second Amendment did not properly apply to the case, as prior caselaw, statute, and the Constitution itself recognized that the District of Columbia is not a state subject to the jurisdiction of the Bill.