US President Joe Biden has said a shock decision by the country's Supreme Court that dials back restrictions on carrying guns "defies common sense".
The ruling by the country's highest legal body comes just weeks after 19 children and two teachers were killed at a school shooting massacre in Uvalde, Texas, and 10 shoppers were shot dead in a supermarket in Buffalo, New York.
The Supreme Court on Thursday (local time) struck down a 100-year-old New York State law that had required people who wanted a gun licence to prove they had "proper cause" to carry a concealed firearm and that they were in "a special or unique" danger.
The Court overturned the law, voting 6-3, saying it violated the Constitutional right to bear arms.
While that case was focused on New York the ruling could also affect several other states, including California and Massachusetts, that have similar restrictions on carrying guns in public.
The court is currently comprised of six conservative-leading judges, and three liberal justices.
Justice Clarence Thomas wrote the majority opinion and was joined by the other five conservatives on the nine-member court, three of whom were nominated by former Republican president Donald Trump.
Thomas said the New York law prevents "law-abiding citizens with ordinary self-defence needs from exercising their Second Amendment right to keep and bear arms in public for self-defence."
"We conclude that the State's licensing regime violates the Constitution," Thomas said.
The ruling is the first by the court in a major Second Amendment case in over a decade, when it ruled in 2008 that Americans have a right to keep a gun at home for self-defence.
Members of the US Supreme Court pose for a group photo. Photo / AP
Biden: Decision 'defies common sense'
President Biden said in a statement that he was "deeply disappointed" in the ruling.
"It contradicts both common sense and the Constitution, and should deeply trouble us all," he added.
"I call on Americans across the country to make their voices heard on gun safety. Lives are on the line."
It was a stunning victory for the National Rifle Association lobby group, which brought the case along with two New York men who had been denied gun permits.
"Today's ruling is a watershed win for good men and women all across America and is the result of a decades-long fight the NRA has led," NRA executive vice president Wayne LaPierre said in a statement.
"The right to self-defence and to defend your family and loved ones should not end at your home."
NRA executive vice president Wayne LaPierre speaks at a group meeting in Houston, Texas. Photo / AP
New York Governor Kathy Hochul called it a "dark day".
"It is outrageous that at a moment of national reckoning on gun violence, the Supreme Court has recklessly struck down a New York law that limits those who can carry concealed weapons," Hochul said.
"This is a dangerous decision from a court hell-bent on pushing a radical ideological agenda and infringing on the rights of states to protect our citizens from being gunned down in our streets, schools, and churches," Californian Governor Newsom tweeted.
The ruling comes as the US Senate is considering a rare bipartisan bill that includes modest gun control measures.
Democratic Senator Dick Durbin said the ruling "makes it all the more important for Congress to take actionable steps to protect our kids and communities from this nation's gun violence epidemic".
- Benedict Brook, news.com.au