As Americans process yet another school shooting, the debate over gun control and the Second Amendment is once again raging in the US.
On Tuesday, a teenage gunman killed 19 young children and two teachers at a Texas primary school, prompting US President Joe Biden to denounce the country's gun lobby and vow to end the cycle of mass shootings.
But despite the tens of thousands of people killed by guns every year, many in the US see gun ownership as a constitutional right, protected by the Second Amendment.
What is the Second Amendment?
The Second Amendment to the US Constitution, ratified in 1791, states: “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.”
The amendment was based on English common law as well as the English Bill of Rights of 1689, which allowed for the possession of weapons for use in self-defence and resistance to oppression.
This concept carried over to the American colonies in the form of the militia, a group made up of able-bodied men obligated to defend a specific territory. Militias became integral during the American Revolution.
Due to fears of a foreign power attempting to invade the young country or that the government would eventually come to oppress its citizens, the Second Amendment was added to the constitution.
The modern application of the amendment has caused a great deal of debate: some Americans believe it gives all citizens the right to own almost any weapon they choose for the purpose of self-defence.
Others say it is antiquated and only applies to those in a “militia” — now the National Guard and other formal military organisations.
Why is the US gun lobby so powerful?
Every year, the US gun lobby spends millions of dollars supporting various politicians at the local, state and federal levels.
The most prominent group within the lobby is the NRA, the National Rifle Association, which bills itself as the country's “oldest civil rights organisation”.
Previously operating more like a club promoting gun ownership for sport, in the 1970s, the NRA became increasingly aligned with the Republican Party after the passing of the Gun Control Act of 1968, which mandated that gun dealers be federally licensed and established restrictions on particular types of firearms.
Over the past several decades, the NRA has poured money into lobbying efforts, backing conservative politicians and fighting against stricter gun control in Congress.
The organisation spent nearly $5 million on lobbying in 2021, website Open Secrets reported.
But the NRA is far from some shadowy organisation funded by big business: while some of the NRA's lobbying money comes from big corporations, including weapons manufacturers, the majority of its funds come from everyday Americans.
Since 2005, the NRA Political Victory Fund, the organisation's political action committee, has received nearly $85m in contributions from individual donors, according to CNNMoney.
The man who killed 19 children and two teachers in Texas bought his guns legally days before the attack, purchasing two rifles from a federally licensed dealer along with 375 rounds of ammunition, AP reported.
The NRA issued a statement about the shooting, saying its "deepest sympathies are with the families and victims involved in this horrific and evil crime".
The organisation also claimed the massacre was "the act of a lone, deranged criminal".