The district said it would appeal Friday's decision, and legal observers predicted the justices are now likely to step in. There is a clear split among the lower courts, and the issue is squarely presented.
Both sides point to language in the amendment itself to support their position.
The residents who challenged the district's law, joined by groups such as the National Rifle Association, said the amendment's language is clear: "The right of the people to keep and bear arms shall not be infringed."
But the district, joined by handgun control groups, argued that the Second Amendment only protects the collective right to bear arms. They contended that the amendment was designed to protect, as the amendment also says, the right of state governments to assemble "a well regulated militia, being necessary to the security of a free state."