"At a time when semi-automatic firearms (which [President Obama and allies] misleadingly call 'assault weapons') are more prevalent than ever before, our nation's murder rate is at a 47-year low, having decreased 52 percent since 1991," Chris W. Cox, the top lobbyist for the National Rifle Association, wrote in December 2011.
But pro-gun control groups pointed to loopholes in the law to say that a stronger ban would be needed to more effectively combat crime. A 2008 study by the Brady Campaign to Prevent Gun Violence found that 168 people were killed and 185 were wounded by assault weapons in the four years following the ban's expiration.
"This now-expired law was limited in scope, and was circumvented by many gun manufacturers; it reduced the use of assault weapons in crime. The experience suggests that a stronger, more comprehensive law would enhance public safety even more," according to the Brady Campaign study.
Sen. Frank Lautenberg (D-N.J.) will introduce legislation that bans the sale of high-capacity magazines in the next Congress, according to The Huffington Post.
The provision was included in the 1994 assault weapons ban and made it illegal to obtain and carry most large-capacity magazines, defined as being capable of holding more than 10 rounds.
The the Connecticut gunman Lanza was reportedly carrying multiple, high-capacity magazines capable of holding up to 30 rounds each. All victims at the school were shot several times with the high-powered rifle.
Connecticut has some of the strictest gun laws in the country, according to the Brady Campaign, including restrictions on the purchase of so-called "assault weapons." But as Bloomberg Businessweek reported Monday, a 2011 effort to ban the possession of high-capacity magazines (that hold more than 10 rounds) failed in the face of pressure from the National Rifle Association.
Supporters of banning high-capacity magazines say that they make it easier to carry out a mass shooting because a gunman could kill more people without having to spend time to reload the weapon. But opponents say that mass shootings have occurred without the use of high-capacity clips, such as the 2007 Virginia Tech shooting in which the gunman used 10- and 15-round magazines, Bloomberg Businessweek reported.
Public officials have also concentrated on mandating tougher enforcement measures that prevent mentally ill individuals from purchasing guns.
In response to the Virginia Tech massacre, President Bush in January 2008 signed into law a measure designed to strengthen the national criminal background check system by ensuring that mental health records that would bar individuals from purchasing guns are included. The bill was supported by the NRA and the Brady campaign. Mentally ill people are barred under law from legally purchasing firearms under the 1993 Brady Handgun Prevention Act, but the background-check's ability to enforce that provision had been considered weak. At the time the bill was signed, 17 states provided no mental health records to the background-check system, according to the Los Angeles Times.
The Virginia Tech shooter had been ordered by a court to enter into mental-health treatment, but his name was never entered into the background-check system, the Times reported, and he was able to legally purchase the two handguns he used in the massacre.