The case arose when Otis McDonald and six other Chicago residents sued the city, arguing that the ordinance, which prohibited the possession of handguns within the city limits, violated their right to keep and bear arms. The plaintiffs argued that the Second Amendment protected their right to possess handguns for self-defense, and that the city's ordinance was a blanket ban on handguns that did not allow for any exceptions.
The City of Chicago argued that the Second Amendment did not protect an individual's right to possess a gun, but rather the collective right of states to maintain militias. The city also argued that the ordinance was necessary to reduce gun violence and protect public safety.
The Supreme Court disagreed with the city's arguments and held that the Second Amendment protects an individual's right to keep and bear arms, including handguns, for self-defense. The Court also held that the city's ordinance was not narrowly tailored to achieve the government's interest in protecting public safety, and therefore violated the Second Amendment.
The McDonald case was significant because it was the first time the Supreme Court had held that the Second Amendment protects an individual's right to possess a handgun for self-defense. The decision has been cited in numerous subsequent cases involving gun control laws.