ProPublica decided to take a look at what's happened legislatively in states where some of the worst shootings in recent U.S. history have occurred to see what effect, if any, those events had on gun laws.
We found that while legislators in Virginia, Alabama, Arizona, New York, Texas and Colorado sometimes contemplated tightening rules after rampage shootings, few measures gained passage. In fact, several states have made it easier to buy more guns and take them to more places.
Here's a rundown of what's happened in each of those states:
Virginia: After 23-year-old Virginia Tech student Seung Hui Cho killed 32 students and faculty members at the university in April 2007, then-Gov. Tim Kaine assigned a blue-ribbon task force to examine gun policies in the state. The task force made dozens of recommendations that, among other things, suggested that the state intensify background checks for gun purchasers, and ban firearm possession on college campuses. None of the recommendations became law.
The most significant change in Virginia came two weeks after the shooting when Kaine signed an executive order requiring the names of all people involuntarily committed to mental health facilities to be provided to a federal database called the National Instant Criminal Background Check System, or NICS. Licensed gun dealers are supposed to check the database before they sell anyone a gun.
President George W. Bush subsequently signed federal legislation requiring all states to submit their mental health records to NICS, but to gain the support of the NRA, Congress agreed to two concessions. It made changes to the way the government defined who was "mentally defective," excluding people, for example, who had been "fully released or discharged" from mandatory treatment. The law also gave mentally ill people an avenue for restoring their gun rights if they could prove to a court that they had been rehabilitated. After the law passed, the NRA pushed state lawmakers to limit roadblocks for people applying to regain their rights.
Virginia is particularly open to restoring peoples' gun rights. A 2011 New York Times investigation found that the restoration process in the state allowed some people to regain access to guns simply by writing a letter to the state. Others were permitted to carry guns just weeks or months after being hospitalized for psychiatric treatment.
This past year the Virginia state legislature repealed a law that had barred people from buying more than one handgun per month — a law put in place because so many guns purchased in Virginia were later used in crimes committed in states with more restrictions.
The legislature also has made several changes to its gun permitting process. In March, the state eliminated municipalities' ability to require fingerprints as part of a concealed weapon permit application. The state used to require gun owners to undergo training with a certified instructor in order to get permits, but in 2009 it adopted a law allowing people to take an hour-long online test instead. Since Virginia adopted the law, the number of concealed handgun permits the state has issued increased dramatically and many of the permits were issued to people who live in other states where Virginia permits are accepted.
In 2010, Virginia became one of five states to allow permit holders to carry concealed and loaded weapons into bars and restaurants.
Alabama: In Alabama, gun control advocates have won two small legislative victories since March 2009, when 28-year-old sausage plant worker Michael McLendon went on a three-town shooting spree, killing 10 people.
In 2011, the state made it illegal for people to buy weapons for someone else who doesn't have permission to carry one or to provide false information about their identity to a licensed gun dealer. The law was intended to help crack down on gun trafficking. (According to data compiled by non-profit Mayors Against Illegal Guns, the state had the fifth highest rate of crime gun exports in 2009.)
After Florida teen Trayvon Martin was shot and killed by neighborhood watch volunteer George Zimmerman in February 2012, the Alabama state legislature made a slight revision to its version of a law known as the "castle doctrine," which is meant to allow property owners to protect their homes against intruders. Alabama changed its law so that a shooter would only be entitled to civil immunity for shooting a trespasser if the property owner reacted "reasonably."
Arizona: After former U.S. Rep. Gabrielle Giffords, D-Ariz., was shot in the head in a hail of bullets that killed six and wounded 13, a bill was introduced in the state legislature to limit gun magazines to 10 bullets, but the bill failed in the face of pressure from the gun lobby. A similar bill was proposed in Connecticut last year; it didn't pass either.
In March 2012, Arizona Gov. Jan Brewer signed a bill with the opposite effect, forbidding the Arizona Game and Fish Commission from limiting magazine capacity for any gun approved for hunting.
According to rankings assembled by the Law Center to Prevent Gun Violence, Arizona is "49th out of 50 — having enacted some of the weakest gun violence prevention laws in the country."
Arizona doesn't require a license to carry a concealed firearm in public, nor does it limit the number of firearms that someone can buy at once.
New York: After a mass shooting at an immigration services center in Binghamton, N.Y., where 13 people were killed and four were wounded, the state assembly entertained several bills on gun control. None passed. One bill would have given police more control over records related to firearm sales. Another would have banned 50-caliber weapons and allowed people to turn them into the state in exchange for fair market value.
Perhaps the most controversial bill in the package would have required the use of a technology called microstamping on all bullets sold in the state.
Using this technology, a serial number could be stamped on bullet casings so they could be traced back to a particular gun. The gun industry argued that the technology would be too expensive and was still unproven. Some gun manufacturers were so upset by it that they threatened to leave the state. The bill passed the Assembly in June, but the Senate did not vote on it.
In January 2012, the legislature repealed a law that previously required handgun manufacturers and dealers to share information about bullet casings and ballistics with the state. Critics of the law said the database used to maintain the information cost too much and didn't help police.
Texas: There's been no effort to tighten gun control in Texas since Army Maj. Nidal Hasan, 39, killed 13 and wounded 32 at a military processing center at Fort Hood in 2009.
In 2011, legislators passed two bills that gave gun carriers greater freedom to take their weapons to more places. One bill restricted employers from prohibiting guns from vehicles in parking areas and another allowed foster parents to carry handguns while transporting their foster children, as long as they are licensed carriers.
Colorado: Colorado's state legislature has not convened since Aurora graduate student James Eagan Holmes, 24, killed 12 and wounded 58 in a movie theater in July. At the time, Colorado Gov. John Hickenlooper suggested that families of victims needed time to grieve before a discussion on gun control could begin in the state.
After the Connecticut shooting, Hickenlooper said that "the time is right" for the state to consider stronger gun control legislation. He has introduced a measure to strengthen background checks for gun buyers.