The gun debate.

• Author: Smith, Patricia
• Position: NATIONAL

Mass shootings have reignited the political fight over gun control. Here's what you need to know to understand the issue.

Last month, following a spate of mass shootings in the U.S., a tearful President Obama announced that he was using his executive powers to try to stem gun violence. The modest steps he announced--the only ones he could take without the approval of Congress--included trying to expand the number of gun sellers required to conduct criminal background checks, pledging to hire more people to carry out those checks, and ordering better tracking of lost guns.

The president's move came a month after a terrorist shooting in December in San Bernardino, California, left 14 people dead. That and other recent shootings, including one in October at a community college in Oregon in which nine people died, have reignited the national debate over gun control.

The U.S. has more guns per capita than any other developed country--and far more gun violence (see chart, p. 11). In 2014, there were more than 33,000 firearm-related deaths in the U.S. The question is whether stricter gun control laws would help lower that number. Congress, like the nation, has long been divided and hasn't passed major gun control legislation in the past two decades.

Here's what you need to know to understand the ongoing debate.

What is gun control?

"Gun control" is a broad term that covers many kinds of restrictions. It can include regulations on what kinds of firearms can be bought and sold, who can possess or sell them, and where and how they can be stored or carried. Gun control can involve the responsibilities a seller has to check a buyer's background and whether a gun sale should be reported to the government. The term also covers limits on types of ammunition and the size of magazines (the part of the gun that holds ammunition).

In recent years, gun control debates have focused on three issues: background checks for buyers, the laws regulating who can carry weapons in public, and the kinds of guns available for purchase. One of the most contentious arguments is over who should be allowed to possess assault rifles--military-style weapons capable of firing multiple bullets quickly; assault rifles have been used in many recent mass shootings.

What's the state of federal gun control today?

Federal law prohibits specific groups of people from owning firearms. The list includes convicted felons, those diagnosed with certain types of mental illness, and immigrants without legal status.

The Brady Handgun Violence Prevention Act, passed by Congress in 1993, requires licensed gun dealers to conduct background checks on potential buyers through an F.B.I. database. This is meant to prevent the sale of guns to someone who's prohibited from owning one.

But the system has major holes in it. Perhaps the biggest is that many small-scale gun sellers claim to be "hobbyists," who aren't required to conduct background checks. Because many of these sellers do business at gun shows, this is often referred to as "the gun show loophole." Another problem: Most people with serious mental illness never receive a diagnosis, so they can still own guns legally.

From 1994 to 2004, federal law banned the sale of many types of assault rifles and high-capacity magazines. Since the law expired, repeated efforts to renew the ban in Congress have failed, but several states have their own bans on assault weapons.

Where does the American public stand?

Gun control is one of the most sharply divisive issues in the U.S. today. When Americans are asked whether they favor stricter gun laws, they're about evenly divided, according to a recent Pew Research Center poll.

Most Democrats and city dwellers favor more restrictions. Most Republicans and people in rural areas--where guns are more common--favor protecting gun rights.

But there's more consensus on some specific measures: When asked in the Pew poll whether private gun sales should be subject to background checks, 88 percent of Democrats and 79 percent of Republicans said they should.

What are the arguments against gun control?

Gun rights advocates see weapon possession as a matter of individual rights. They say that people have the right to arm themselves for hunting, self-defense, and sport--or just because they want to.

Rather than being a danger, gun owners say, weapons can make society safer. They say guns give people the power of self-defense--and dissuade criminals from victimizing people who might be armed.

"The only thing that stops a bad guy with a gun is a good guy with a gun," Wayne LaPierre of the National...