The Assault Weapons Ban: What Was It and Did It Work?

Dec. 18, 2012 -- Editor's Note: This post is part of a larger series by ABC News examining the complex legal, political and social issues in the gun control debate. The series is part of ABC's special coverage of the search for solutions in the wake of the tragedy at Sandy Hook Elementary School in Connecticut.

When the 113th Congress is sworn in in January, expect the debate over gun control to have renewed urgency. Several prominent lawmakers have already come forth to call for a re-examination and re-working of our nation's gun laws in the wake of Friday's mass shooting at an elementary school in Newtown, Conn.

While new legislation likely won't be introduced until after Jan. 3, statements from top Senators such as Dianne Feinstein (D-Calif.) and Frank Lautenberg (D-N.J.) suggest that new proposals could be similar to the Federal Assault Weapons Ban that was in in place from 1994 to 2004.

"I can tell you that he is going to have a bill to lead on because as a first-day bill I'm going to introduce in the Senate and the same bill will be introduced in the House -- a bill to ban assault weapons," Feinstein said on NBC's "Meet the Press."

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"High-capacity magazines -- devices that dramatically boost a weapon's firing power -- were prohibited from 1994 until 2004, when the federal assault weapons ban was in place... It's time to end the bloodshed and restore common sense to our gun laws -- beginning with a permanent ban on high-capacity gun magazines," Lautenberg wrote in an op-ed on the Huffington Post that he penned with Democratic Congresswoman Carolyn McCarthy, whose husband was killed in the Long Island Railroad shooting of 1993.

What Did the Assault Weapons Ban Do?

Passed by Congress on Sept. 13, 1994, and signed by Bill Clinton later that day, the Federal Assault Weapons Ban prohibited the manufacturing of 18 specific models of semiautomatic weapons, along with the manufacturing of high-capacity ammunition magazines that could carry more than 10 rounds. The ban had a provision that allowed it to expire in September 2004.

Several attempts were made in Congress to re-up the ban, the most recent in June 2008, according to the Library of Congress, but none of them have been successful. Republicans generally opposed it; high-profile Democrats typically shied away from the issue.

In the second presidential debate of the 2012 campaign, President Obama said he was interested in re-instituting the ban.

"Weapons that were designed for soldiers in war theaters don't belong on our streets. And so what I'm trying to do is to get a broader conversation about how do we reduce the violence generally," the president said. "Part of it is seeing if we can get an assault weapons ban reintroduced."

Could a Ban Have Prevented the Connecticut Shootings?

It's impossible to say for sure, but it seems unlikely that if the law were still in place, as it was written, it could have done much to prevent Friday's tragedy. Lanza's primary weapon, the Bushmaster .223 rifle, is a type of AR-15 semiautomatic rifle, certain models of which were prohibited from being sold under the ban, but the Bushmaster model used by Lanza was not on that list.

Additionally, the language in the law was loose enough that a gun enthusiast who was interested in adding a type of AR-15 to their collection could have purchased one legally.

What's more, the other two firearms found at the scene -- a Glock handgun and a Sig Sauer handgun -- were also not affected by the ban.

Was the Ban Effective at Reducing Gun Violence In General?

That is unclear. According to a 2004 study from the University of Pennsylvania, the number of people killed in mass shootings did go down generally during the years that the ban was in effect. The exception was 1999, the year that the shooting at Columbine High School happened.

The number of mass shootings per year has doubled since the ban expired, but the researchers say it's difficult to discern whether there was a cause-and-effect relationship.

The study found that gun crimes involving assault weapons declined by as much as 72 percent in the localities examined after the ban went into effect. However, the authors note that these types of weapons were only used in 2 to 8 percent of the gun crimes committed prior to the ban, so the larger impact on gun violence was minimal.

"We cannot clearly credit the ban with any of the nation's recent drop in gun violence," the study concluded. "And, indeed, there has been no discernible reduction in the lethality and injuriousness of gun violence."

Gun control proponents argued the assault weapons ban was too narrow, and its language was too lenient. There were hundreds of assault weapons unaffected by the law, they said, and many loopholes that allowed for the continued manufacturing of models similar to those banned.