President Barack Obama has unveiled his gun control plans. He has said that the US must do more to protect American children, after the shooting at a school in Newtown, Connecticut.
Twenty children and six women died in the assault on Sandy Hook school last month by a lone man who then took his own life.
The gunman has been identified by police as Adam Lanza, 20, who shot dead his mother before driving to the school in her car.
Officials say he was armed with hundreds of rounds of ammunition, and used a semi-automatic rifle as his main weapon. He was also carrying two handguns, and a shotgun was recovered from a car.
New rules described as the toughest in the US were introduced in New York state on Tuesday.
US history of gun law and rules
Any law-abiding citizen in the United States is allowed to own or carry a gun.
That right comes from the US Bill of Rights and the second amendment to the United States Constitution, the country's supreme law, which was written in 1791.
It reads: "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Anyone over the age of 18 is allowed to buy a rifle or shotgun from a licensed dealer in any state with over-21s able to buy handguns too.
Certain people are banned from owning weapons including convicted criminals, people with mental health illnesses or non-US citizens.
There are also special rules banning guns in and near schools.
Controversy and debate
There has been a lot of debate about the right to own and carry guns in America, mostly after mass shootings.
Last year, James Eagan Holmes, 24, opened fire at a screening of Dark Knight Rises in Aurora, Colorado, killing 12 people and injuring 58.
Holmes was armed with a number of guns - all of which he bought legally.
Oscar-winning documentary-maker Michael Moore made a film about the issue following the Columbine school shootings in 1999.
Two students shot 13 people dead and wounded 23 others before killing themselves.
There was more debate after the 2007 Virginia Tech shootings in which 32 people died.
In its most simple terms, those opposed to gun use and ownership say fewer people would die if there were tighter controls.
They point to the high number of people killed in the United States every year compared to countries where people aren't allowed to own guns.
Those in favour argue that American citizens should be allowed to defend themselves, especially in more rural and less populated areas of the country and that it is their right under the second amendment.
They also say that if guns were banned only criminals would be armed.
The issue of gun control and ownership was not a priority for either of the two main candidates for president - Mitt Romney and Barack Obama at last year's US election.
Groups such as the wealthy National Rifle Association (NRA) and the Gun Owners of America (GOA) often mobilise voters and politicians to back existing gun laws and argue against anti-gun lobbies.
Politicians fear arguing against those organisations could lose them votes.
The Brady Campaign is the largest US group campaigning for the restriction of guns.