28 CFR § 25.4 - Record source categories.

It is anticipated that most records in the NICS Index will be obtained from Federal agencies. It is also anticipated that a limited number of authorized state and local law enforcement agencies will voluntarily contribute records to the NICS Index. Information in the NCIC and III systems that will be searched during a background check has been or will be contributed voluntarily by Federal, state, local, and international criminal justice agencies.