Proposals for universal background checks would require almost all firearms transactions in the United States to be recorded and go through the National Instant Criminal Background Check System (NICS), closing what is sometimes called the private sale exemption. Universal background checks are not required by U.S. federal law, but at least 21 states and the District of Columbia currently require background checks for at least some private sales of firearms.
Background
Federal law requires background checks (through the National Instant Criminal Background Check System) only for guns sold through licensed firearm dealers, which account for 78% of all gun sales in the United States. This figure was published in a 2017 study by the Annals of Internal Medicine which, using a 2015 survey, found that 22% of recent gun transfers (purchased and nonpurchased) were completed without a background check. The authors noted that while this number was less than in years past, it nonetheless indicates that millions of American adults are able to obtain firearms without background checks. The current federal law allows people not "engaged in the business" of selling firearms to sell firearms without a license or records. A 2008 report from the Coalition to Stop Gun Violence (CSGV) stated that the National Instant Criminal Background Check System had prevented over 1.4 million felons and other prohibited persons from purchasing firearms in the years between 1994-2005. According to the CSGV, the law also has a prohibitive effect, that deters illegal purchases.
In November 1998, President Bill Clinton directed the U.S. Secretary of the Treasury and the U.S. Attorney General (A.G.) to provide recommendations concerning the fact that 25 percent or more of sellers at gun shows are not required to run background checks on potential buyers. This was called the gun show loophole. Two months later, Gun Shows: Brady Checks and Crime Gun Traces was released. The Secretary and the A.G. made seven recommendations, including expanding the definition of "gun show," and reviewing the definition of "engaged in the business".
After the Columbine High School massacre in April 1999, gun shows and background checks became a focus of national debate. In May, the executive vice president of the National Rifle Association (NRA) told the House Judiciary Subcommittee on Crime, "We think it is reasonable to provide mandatory, instant criminal background checks for every sale at every gun show." Those concerned about the shows believed they were a source of illegally trafficked firearms. Efforts to reverse a key feature of the Firearm Owners Protection Act (FOPA) by requiring criminal background checks and purchase records on private sales at gun shows, which had become prolific in the U.S. since the law's passage in 1986, were unsuccessful.
Private sale exemption
On August 5, 2010, issue of The New England Journal of Medicine, researchers Garen J. Wintemute, Anthony A. Braga, and David M. Kennedy, wrote that gun shows account for only a fraction of all U.S. gun sales and that a more effective strategy would be to make all private-party gun sales go through the screening and record-keeping processes that FFL dealers are required to do. Their report concluded:
Following the December 14, 2012 Sandy Hook Elementary School massacre, there were numerous calls for universal background checks to close what is now referred to as the "private sale loophole." In an essay published in 2013, Wintemute said that comprehensive background checks that included private sales would result in a simple, fair framework for retail firearms commerce. In February 2014, researchers at the Johns Hopkins Center for Gun Policy and Research reported that after the 2007 repeal in Missouri of a long-standing law that required all handgun buyers to pass a background check there was a 23 percent increase in firearms homicides.