Legal Sidebari

Privately Made and Unmarked Firearms:
Overview of ATF “Ghost Gun” Rule
April 25, 2022
On April 7, 2021, President Biden announced several executive actions seeking to address gun violence,
including instructions for the Department of Justice (DOJ) to issue a rule addressing so-called “ghost
guns” that lack serial numbers or other identifying markings. The announcement came amidst concern
from the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) over its inability to trace unmarked
firearms that have been used in shootings and other crimes in recent years.
In May 2021, ATF published a proposed rule addressing certain regulatory definitions relevant to
identification requirements for firearms, among other things. On April 11, 2022, DOJ submitted ATF final
rule 2021R-05F, “Definition of ‘Frame or Receiver’ and Identification of Firearms,” with the stated goal
of “ensur[ing] the proper marking, recordkeeping, and traceability of all firearms manufactured, imported,
acquired and disposed by” persons and entities federally licensed to engage in the firearms business
(Federal Firearms Licensees, or “FFLs”). This Sidebar provides legal context for, and an overview of, the
major components of the recent final rule.
Overview of Existing Firearm Identification Requirements
By statute, FFLs are required to “identify by means of a serial number engraved or cast on the receiver or
frame of the weapon” each firearm manufactured in, or imported into, the United States. Existing
regulations establish more detailed requirements for how the serial number must be affixed, including the
minimum depth and print size, and require additional information such as the firearm model, caliber or
gauge, and the FFL’s name and business location. Under the statutory definition of the term firearm, these
identification requirements extend to firearm “frames or receivers.” The term frame or receiver is
separately defined in regulations as “[t]hat part of a firearm which provides housing for the hammer, bolt
or breechblock, and firing mechanism, and which is usually threaded at its forward portion to receive the
barrel.” As described by ATF, a “frame or receiver” is essentially “the primary structural component[] of a
firearm to which fire control components are attached.” The firearm identification requirements in statute
and regulation facilitate ATF’s ability to trace firearms that are lost or used in crimes, as the chain of
custody and distribution may be established using FFLs’ required records.
Not all firearms in the United States are subject to the identification requirements described above,
however. First, the requirements apply only to FFLs, meaning that individuals who wish to make their
Congressional Research Service
https://crsreports.congress.gov
LSB10733
CRS Legal Sidebar
Prepared for Members and
Committees of Congress

---

Congressional Research Service
2
own firearms for personal use need not identify or mark them. The process of making one’s own firearm
that is not subject to identification requirements has been increasingly facilitated in recent years by the
commercial availability of “parts kits” that include firearm components and tools with which a functional
weapon can be completed and assembled relatively quickly and easily. Some of these parts kits may
include certain unfinished frames or receivers—sometimes referred to as “blanks,” “billets,” “castings,”
“machined bodies,” or “80%” receivers—that ATF has not previously considered to have reached a stage
of manufacturing that would make them subject to federal requirements such as interstate commerce
restrictions, background checks, or marking obligations. Such components have been sold commercially,
individually or in parts kits, without meeting such requirements.
Additionally, ATF’s current definitions of frame or receiver do not expressly cover many types of
firearms that, for instance, have receivers in multiple pieces or otherwise do not incorporate all of the
components in the definitional language. According to ATF, such firearms now “constitute the majority of
firearms in the United States.” Thus, if read strictly, as some courts have done, the current definitional
language could mean that many U.S. firearms would lack a frame or receiver currently subject to
regulation, and manufacturers of split or multi-piece receivers would not need to comply with marking,
background check, licensing, and recordkeeping requirements.
Privately made firearms that enter the stream of commerce without markings useful in tracing them, and
that are subsequently used illicitly and recovered by law enforcement, are sometimes referred to as “ghost
guns.” ATF and other law enforcement authorities have expressed concern that the commercial
availability of parts kits with unmarked, unfinished firearm frames or receivers could facilitate access to
firearms by persons prohibited from possessing them, given that such kits can be sold without a
background check. Conversely, others have suggested that the importance of serial numbers in firearm
tracing is overstated and that additional marking requirements would be onerous and unnecessary.
ATF’s April 2022 Final Rule
Primarily, ATF’s April 2022 final rule makes changes to current regulatory definitions and requirements
relevant to homemade and unmarked firearms. First, the rule amends ATF’s regulatory definitions of
frame or receiver to account for developments in firearms technology described above. The rule updates
the regulatory definitions with separate sub-definitions for handgun “frames,” non-handgun “receivers,”
and mufflers or silencers to clarify which part of each item will be considered either the frame or receiver,
and it provides specific examples and pictures. Most existing ATF classifications of particular parts as
frames or receivers are grandfathered in and will continue to be considered frames or receivers, as they
were classified prior to publication of the rule. The new rule also expressly provides for how to mark for
identification a “multi-piece frame or receiver,” meaning a frame or receiver “that may be disassembled
into multiple modular subparts.” Under the rule, “the modular subpart that is the outermost housing or
structure designed to house, hold, or contain” certain other components is the subpart of a multi-piece
frame or receiver that must be identified.
With respect to firearm component kits and unfinished frames or receivers, the rule first amends the
regulatory definition of firearm to include a “weapon parts kit that is designed to or may readily be
completed, assembled, restored, or otherwise converted to expel a projectile by the action of an
explosive.” Regulatory definitions of frame or receiver also now include “a partially complete,
disassembled, or nonfunctional frame or receiver, including a frame or receiver parts kit, that is designed
to or may readily be completed, assembled, restored, or otherwise converted to function as a frame or
receiver.” Articles that have “not yet reached a stage of manufacture” where they are “clearly identifiable
as” unfinished component parts of weapons (such as unformed blocks of metal or raw materials) are
excluded. The term readily is further defined as a “process, action, or physical state that is fairly or
reasonably efficient, quick, and easy” (though not necessarily the most efficient, fastest, or easiest), and
considers other factors such as the expertise and equipment required, parts needed and ease of acquiring

---

Congressional Research Service
3
them, scope, feasibility, and expense. Among other things, persons seeking ATF classification of a
partially complete, disassembled, or nonfunctional item or parts kit to determine whether it meets the new
regulatory definitions must also include any associated templates, jigs, molds, equipment, tools,
instructions, guides, or marketing materials that are made available by the seller. ATF, in turn, may
consider the information or associated items provided in determining whether the submitted item or kit is
a “frame or receiver.” And classification decisions from prior to the rule’s publication will not continue to
be valid with respect to determinations that particular partially complete, disassembled, or nonfunctional
frames or receivers, including parts kits, did not constitute or include frames or receivers.
With supplemented definitions in place, the rule adds requirements and clarifying language to facilitate
the identification and tracing of parts kits, frames or receivers, and unmarked firearms that come into an
FFL’s inventory. FFLs are currently required to comply with recordkeeping requirements related to their
businesses, including maintaining records reflecting certain information (e.g., model and serial number)
about the firearms possessed in inventory, received, and disposed of and completing records of firearm
transactions with unlicensed persons. The rule supplements those requirements in the case of unmarked
firearms and establishes express requirements for marking such firearms when received by an FFL. First,
the rule requires FFLs to mark, or supervise the marking of, the frame or receiver of each “privately made
firearm” that the FFL acquires within 7 days of acquisition or prior to further transfer, whichever is
sooner. Privately made firearms acquired before the effective date of the rule must be marked within 60
days of the effective date or prior to final disposition, whichever is sooner. The term privately made
firearm is defined as a “firearm, including a frame or receiver, completed, assembled, or otherwise
produced by a person other than a licensed manufacturer, and without a serial number placed by a
licensed manufacturer at the time the firearm was produced.” To facilitate access to marking, the rule
amends certain regulatory terms to permit gunsmiths to provide professional marking services for
privately made firearms. Additionally, the rule makes amendments to the regulations regarding FFL
recordkeeping in order to clarify when and how, among other things, privately made firearms received in
an FFL’s inventory are to be recorded and to require maintenance of FFL records indefinitely for tracing
purposes (rather than the previously required 20 years).
Considerations for Congress
The new regulatory language and definitions appear to include as “firearms,” subject to federal
identification and background check requirements, among other things, the kinds of parts kits with
unfinished receivers that have previously been commercially available for home completion without
meeting those requirements. Additionally, the rule establishes express obligations for the marking and
recordkeeping of privately made firearms by FFLs in order to facilitate tracing when unmarked firearms
pass through an FFL’s inventory and are subsequently tied to criminal conduct. The rule does not require
private, unlicensed persons to mark or otherwise comply with new requirements regarding firearms they
make at home for personal use, nor are FFLs required to take possession of unmarked firearms to identify
them. To the extent such firearms must be marked and recorded under the rule, the onus falls on FFLs
who manufacture or sell items or parts kits that are now expressly defined as “firearms” or who
voluntarily receive unmarked firearms in their inventories.
As an executive-branch action implementing statutory terms and requirements, ATF’s new rule is subject
to alteration or rescission by a future Administration (assuming compliance with legal requirements such
as the Administrative Procedure Act). Some state and local laws may further regulate the making or
possession of unmarked firearms. Additionally, Congress may opt to consider legislation codifying, or
limiting, aspects of the rule should it agree or disagree with ATF’s action. For instance, several bills
introduced in the 117th Congress would seek to curtail so-called “ghost guns” or untraceable firearms in
various ways, such as by amending the statutory definition of firearm or prohibiting most transfers and
possession of unmarked firearms. Codifying further restrictions on unmarked firearms could help avoid

---

Congressional Research Service
4
any potential litigation challenging the rulemaking process or scope of authority surrounding ATF’s recent
final rule. Conversely, should Congress determine that the new rule sweeps too broadly, it could consider
legislation defining terms such as firearm and frame or receiver to exclude certain kinds of parts kits or
unfinished firearm components, which would supersede ATF’s regulatory definitions.
The final rule is effective 120 days from the date of publication in the Federal Register.

Author Information

Michael A. Foster

Legislative Attorney




Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff
to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of
information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role.
CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United
States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However,
as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the
permission of the copyright holder if you wish to copy or otherwise use copyrighted material.

LSB10733 · VERSION 1 · NEW

---