The major decision by the US high court is expected to allow more people to carry guns legally.
The US Supreme Court has struck down a New York law restricting gun-carrying rights, in its most important judgement on guns in over a decade.
It expands gun rights amid a fierce national debate over the issue.
The decision, which jeopardises similar regulations in states like California and New Jersey, is expected to allow more people to carry guns legally.
About a quarter of Americans live in states that could be affected if their own rules are challenged
The court found that a New York law requiring residents to prove "proper cause" to carry concealed firearms in public violates the US Constitution.
Justice Clarence Thomas, writing on behalf of the six conservative judges who make up the court's majority, ruled that Americans have a right to carry "commonly used" firearms in public for personal defense.