The Brady Handgun Violence Prevention Act of 1994 is a federal law requiring that all prospective purchasers of firearms be approved through an "instant background check." The background check is performed by licensed gun dealers using a telephone or computer through the National Instant Criminal Background Check System (NICS). To accomplish this, the NICS Operations Center searches three separate databases:

• The NICS Index, which contains records on persons known to be disqualified under federal law from possession of firearms;
  
  
• the National Crime Information Center, a computerized information system of criminal justice data established by the FBI, which contains records on protective orders, deported felons, and fugitives from justice; and
  
  
• the Interstate Identification Index, which contains criminal history records.

Possible results of a Brady Act background check can be:

• "Proceed" means that no disqualifying or negative information is in the system to indicate that a firearm purchase would be unlawful and the transaction may proceed.
  
  
• "Denied" means that the purchase would be unlawful and prohibits the FFL from transferring the firearm to the purchaser.
  
  
• "Delayed" means that the transferee must delay the transaction until contacted again by NICS or 3 business days have elapsed. 10 If NICS does not provide a response after 3 business days, the FFL may transfer the firearm.

The laws of some states also require background searches of their own available criminal databases, as well as mandatory waiting periods prior to delivery of a firearm. 

Bureau of Alcohol, Tobacco and Firearms (ATF) regulations implementing the Brady Act provide that before a licensed dealer may sell or deliver a firearm, the prospective purchaser must provide photo-identification issued by a government entity. The identification must contain the purchaser's name, state of residence, age, gender, and race.