The NICS system uses a number of databases in addition to the criminal history database(s).
www.fbi.gov/hq/cjisd/nics.htmRecord information that would exhibit and/or clarify an individual's prohibitive status pursuant to the Brady Act is vital to the NICS in order to determine subject eligibility to receive and/or possess a firearm. Records contained within the databases searched by the NICS include those of the Interstate Identification Index (e.g., millions of criminal history records), the National Crime Information Center (e.g., protection orders and active felony or misdemeanor warrants) and the NICS Index, a database created solely for the use of the NICS which contains information provided by local, state and federal agencies pertaining to persons prohibited under federal law from receiving or possessing a firearm. Additionally, and as mandated by ATF Regulations, a fourth search of the applicable databases via the Department of Homeland Security's Bureau of Immigration and Customs Enforcement will be conducted for background checks initiated on all non-United States citizens.
The federally prohibitive criteria outlining the reasons an individual may be precluded from the transfer/possession of a firearm or firearm-related permit, pursuant to Title 18 of the United States Code, Section 922 (g) and (n), are as follows:
• A person convicted of/under indictment for a crime punishable by imprisonment for a term exceeding one year, whether or not sentence was imposed. This includes misdemeanor offenses with a potential term of imprisonment in excess of two years, whether or not sentence was imposed.
• Persons who are fugitives from justice; for example, the subject of an active felony or misdemeanor warrant.
• An unlawful user and/or an addict of any controlled substance; for example, a person convicted for the use or possession of a controlled substance within the past year, or a person with multiple arrests for the use or possession of a controlled substance within the past five years with the most recent arrest occurring within the past year, or a person found through a drug test to use a controlled substance unlawfully, provided the test was administered within the past year.
• A person adjudicated mental defective or involuntarily committed to a mental institution or incompetent to handle own affairs, including dispositions to criminal charges of found not guilty by reason of insanity or found incompetent to stand trial.
• An alien illegally/unlawfully in the United States or a non-immigrant who does not qualify for the exceptions under Title18 U.S.C. Section 922(y); for example, not having possession of a valid hunting license.
• A person dishonorably discharged from the United States Armed Forces.
• A person who has renounced his/her United States citizenship.
• The subject of a protective order issued after a hearing in which the respondent had notice that restrains them from harassing, stalking, or threatening an intimate partner or child of such partner. This does not include ex parte orders.
• A person convicted in any court of a misdemeanor crime which includes the use or attempted use of physical force or threatened use of a deadly weapon and the defendant was the spouse, former spouse, parent, guardian of the victim, by a person with whom the victim shares a child in common, by a person who is cohabiting with or has cohabited in the past with the victim as a spouse, parent, guardian or similar situation to a spouse, parent or guardian of the victim.