Biden urged action to prevent gun violence in an emotional message to the nation from the White House, blaming gun manufacturers and their backers for obstructing legislation in Washington.

He said: “When in God’s name are we going to stand up to the gun lobby? Why are we willing to live with this carnage? Why do we keep letting this happen?

The two tragedies serve as depressing reminders of the regularity and savagery of an epidemic of mass gun violence in the United States.

So what can be done about it? What needs to change?

Here is an overview of the current state of America’s gun laws.

The manufacturing, trading, possession, transfer, record keeping, transport, and destruction of firearms, ammunition, and firearms accessories are all regulated by law in the United States under federal legislation.

State agencies and the federal Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) enforce these laws.

In addition to federal gun restrictions on a national level, all state governments and certain local governments have their own laws that regulate firearms more strictly.

Initially, it was believed that while the federal government could not outright outlaw guns, states and cities could.

However, the Supreme Court ruled in McDonald v. City of Chicago in 2010 that states and cities also may not totally prohibit firearms, and the Second Amendment to the United States Constitution guarantees the freedom to keep and bear weapons to every American citizen.

This has been interpreted to suggest that almost everyone can own a gun, however this is not entirely accurate.

Although total gun prohibition is no longer possible, local governments can prohibit the sale and use of specific types of firearms, such as those that discharge a large number of rounds quickly.

Certain types of people are prohibited from buying, selling, using, owning, receiving, transporting, carrying, possessing, or exchanging firearms or ammunition under the US Gun Control Act of 1968.

These include any individual who:

Of course, individuals can often slip through the cracks, and checks and balances could always be tighter; a number of legal loopholes exist, often exploited by gunmen.

Despite tens of millions of background checks being conducted annually, approximately 5,000 to 6,000 prohibited people are convicted of receiving or possessing a handgun each year, according to the US Sentencing Commission.

One thing that doesn’t help the situation is the complexity in the variation of gun laws across America.

State laws vary greatly and are separate from existing federal gun regulations; they are frequently less stringent than federal firearms rules, and state and local law enforcement agencies are not legally obligated to enforce federal restrictions.

The right to keep and bear arms is protected in 44 states by state constitutions that are analogous to the Second Amendment of the United States Constitution – California, Iowa, Maryland, Minnesota, New Jersey, and New York are the exceptions.

Owners of firearms are subject to the firearm laws of the state they are in, not just their home state.

Reciprocity exists across states in specific circumstances, such in regards to concealed carry permits, which allow a person to carry a firearm in public in a concealed manner.

Idaho, for example, will accept an Oregon permit, but Oregon will not accept an Idaho permit, and while Florida allows concealed carry of both weapons and firearms, most states only allow concealed carry of firearms.

Some states do not recognise out-of-state permits to carry a firearm, so knowing the regulations of each state before travelling with a handgun is critical.

It’s not quite as simple as the President signing off on new legislation to prohibit guns on a national scale.

Since bipartisan efforts to tighten background checks on guns purchases fell in the aftermath of the 2012 Sandy Hook tragedy (which birthed the controversial phrase, “The only thing that stops a bad guy with a gun, is a good guy with a gun”), the US Congress has been unable to implement significant gun legislation.

That’s because it is made up of two diametrically opposed sides – Democrats and Republicans – that rarely agree on anything.

That means reaching vote thresholds needed to pass any bills are often not met, since Republicans especially vote against gun control reforms, while Democrats back them.

Because Washington is deadlocked on the subject, most gun legislation takes place at the state level.

Democrats believe that this intransigence necessitates a change in Senate rules, but that’s just another point on which politicians will disagree.

The National Rifle Association (NRA) – a gun rights advocacy group among the most influential in US politics – plays a large part too.

The group has influenced legislation, participated in or instigated lawsuits, and endorsed or opposed political candidates at state and federal levels throughout its history.

It has frequently been targeted by gun control groups, political commentators, and politicians in the aftermath of high-profile shootings, and since the 1990s, the NRA has been increasingly closely associated with the Republican party.