Since the 1994 inception of the National Instant Criminal Background Check System, mandated by the Brady Handgun Violence Prevention Act, approximately 976,000 of the 45.7 million background checks conducted resulted in rejections -- an aggregate rejection rate of 2.1 percent.
The Brady Act requires that a background check be conducted by the FBI or a state agency prior to the transfer of a firearm from a federally licensed dealer to a purchaser. The Act established the National Instant Criminal Background Check System (or NICS) in which about half the checks nationwide are conducted by the FBI and half by state agencies. In May 2003, the FBI reported that under a new process for conducting the checks implemented in mid-2002, an immediate determination of applicant eligibility to purchase a firearm is now occurring in more than 90 percent of background queries.
For the first time since the Act took effect, more prospective firearms purchasers were rejected during 2002 for reasons other than a felony conviction history. The most common reason for denial for a non-felony background was having a prior conviction for a misdemeanor offense involving domestic violence.
Who Cannot Buy a Gun in America?
Under the Federal Gun Control Act, 18 U.S.C. Section 922, a firearm may not be sold or transferred to a person who --
In addition, the statute makes it unlawful for any licensed importer, manufacturer, dealer or collector to transfer a long gun to a person younger than 18 years old or any other type of firearm to a person less than 21 years old.
The Brady act allows the FBI three business days to complete a background check. If the check cannot be completed in three business days, the sale or transfer may be completed although potentially disqualifying information might exist in the NICS. (Also See: Possible Outcomes of a Brady Background Check)

