Explainer: Why tighter U.S. firearm laws are unlikely

“Gun violence in this country is an epidemic and it’s an international embarrassment.”

President Joe Biden promised to tighten gun laws but he’ll find it difficult to make good on that ambitious pledge, despite widespread public support.

The United States has more guns than people.

For every 100 residents, there are about 121 firearms in circulation, making the U.S. by far the most heavily armed society in the world.

That figure belies the fact that gun ownership is actually becoming less common.

Nearly a half of households owned firearms in 1990.

That had dropped to a third by 2016.

But ownership varies greatly state by state.

In New Jersey, for example, 8% of households have guns.

In Montana, it’s 66%.

The U.S. Constitution enshrines the "right to bear arms".

That's been interpreted to allow individuals to keep handguns at home for self defense - a right cherished by gun advocates.

The federal government requires a criminal background check for most gun buyers, though and tightly regulates the ownership of fully automatic machine guns and silencers.

Most other gun laws are set at the state level, where policies vary widely.

Many Democratic-dominated states, like California, have tightened their laws.

Rural and Republican-dominated states, such as Mississippi, are much more permissive.

Most Americans do support tougher gun laws, according to Reuters/Ipsos polling.

But politicians in Washington have done little on the issue in recent years.

One reason why?

Those small, rural states where gun ownership is widespread have disproportionate influence in the U.S. Senate.

[President Joe Biden, saying:] “This is not it and should not be a partisan issue. This is an American issue.”

In March, the House of Representatives, which is controlled by Democrats, passed legislation to expand background checks.

But it faces long odds in the Senate, which is split 50-50 with Republicans.

[Senate Majority Leader Chuck Schumer, saying:] "No more hopes and prayers, thoughts and prayers. A vote is what we need.”

Presidents can act on their own.

After 2018’s mass shooting in Las Vegas, which killed 58 people, Donald Trump banned what are called "bump stocks” - a gun part that allows semi-automatic rifles to fire at a similar rate to fully automatic ones.

For Biden, the focus is on so-called "ghost guns".

[President Joe Biden, saying:] "These are guns that are homemade, built from a kit that include directions and how to finish the firearm. You can go buy the kit. They have no serial numbers. So when they show up at a crime scene, they can't be traced. “

It seems the political landscape may be shifting.

The National Rifle Association was one of the most powerful lobbying groups, but its hold is potentially waning.

In 2016, it gave $55 million to presidential and congressional candidates.

In 2020, it was $30 million.

Meanwhile gun-control groups, like Moms Demand Action, have stepped up lobbying expenses over the past decade - though they still trail gun-rights groups as a whole.