D prohibits the possession of handguns. It is a crime to carry an unregistered firearm, and the registration of handguns is prohibited. D also requires residents to keep their lawfully owned firearms, such as registered long guns, “unloaded and dissembled or bound by a trigger lock or similar device” unless they are located in a place of business or are being used for lawful recreational activities. P is a D. C. special police officer authorized to carry a handgun while on duty at the Federal Judicial Center. He applied for an exception certificate for a handgun that he wished to keep at home. D refused. P sued on Second Amendment grounds, to enjoin D from enforcing the bar on the registration of handguns, the licensing requirement insofar as it prohibits the carrying of a firearm in the home without a license and the trigger-lock requirement insofar as it prohibits the use of “functional firearms within the home.” The District Court dismissed the complaint. The Court of Appeals reversed. It held that the Second Amendment protects an individual right to possess firearms and that the city’s total ban on handguns, as well as its requirement that firearms in the home be kept nonfunctional even when necessary for self-defense, violated that right. The Court of Appeals directed the District Court to enter summary judgment for P. The Supreme Court granted certiorari.