26 U.S.C. § 5841 : US Code - Section 5841: Registration of firearms

    (a) Central registry
      The Secretary shall maintain a central registry of all firearms
    in the United States which are not in the possession or under the
    control of the United States. This registry shall be known as the
    National Firearms Registration and Transfer Record. The registry
    shall include - 
        (1) identification of the firearm;
        (2) date of registration; and
        (3) identification and address of person entitled to possession
      of the firearm.
    (b) By whom registered
      Each manufacturer, importer, and maker shall register each
    firearm he manufactures, imports, or makes. Each firearm
    transferred shall be registered to the transferee by the
    (c) How registered
      Each manufacturer shall notify the Secretary of the manufacture
    of a firearm in such manner as may by regulations be prescribed and
    such notification shall effect the registration of the firearm
    required by this section. Each importer, maker, and transferor of a
    firearm shall, prior to importing, making, or transferring a
    firearm, obtain authorization in such manner as required by this
    chapter or regulations issued thereunder to import, make, or
    transfer the firearm, and such authorization shall effect the
    registration of the firearm required by this section.
    (d) Firearms registered on effective date of this Act
      A person shown as possessing a firearm by the records maintained
    by the Secretary pursuant to the National Firearms Act in force on
    the day immediately prior to the effective date of the National
    Firearms Act of 1968 (!1) shall be considered to have registered
    under this section the firearms in his possession which are
    disclosed by that record as being in his possession.

    (e) Proof of registration
      A person possessing a firearm registered as required by this
    section shall retain proof of registration which shall be made
    available to the Secretary upon request.