Colo. Rev. Stat. § 18-12-111.5 – Unlawful conduct involving an unserialized firearm, frame, or receiver - exceptions - penalties - authority to serialize a firearm.

(1)
1. (a) A person shall not knowingly possess or transport an unfinished frame or receiver; except that it is not an offense if the unfinished frame or receiver is required by federal law to be imprinted with a serial number and has been imprinted with a serial number by a federal firearms licensee pursuant to federal law or subsection (7) of this section.
2. (b) This subsection (1) does not apply to a federally licensed firearm importer or federally licensed firearm manufacturer acting within the scope of the importer's or manufacturer's license.
(2)
1. (a) A person shall not knowingly sell, offer to sell, transfer, or purchase an unfinished frame or receiver; except that it is not an offense if the unfinished frame or receiver is required by federal law to be imprinted with a serial number and has been imprinted with a serial number by a federal firearms licensee pursuant to federal law or subsection (7) of this section.
2. (b) This subsection (2) does not apply to:
  1. (I) A sale, offer to sell, transfer, or purchase if the purchaser is a federal firearms licensee; or
  2. (II) A temporary transfer to a federal firearms licensee for the purpose of having the firearm or frame or receiver of a firearm imprinted with a serial number pursuant to subsection (7) of this section.
(3)
1. (a) A person shall not knowingly possess, purchase, transport, or receive a firearm or frame or receiver of a firearm that is not imprinted with a serial number by a federal firearms licensee authorized to imprint a serial number on a firearm, frame, or receiver pursuant to federal law or subsection (7) of this section.
2. (b) This subsection (3) does not apply if:
  1. (I) The person possessing, purchasing, transporting, or receiving the firearm or the frame or receiver of a firearm is a federally licensed firearm importer or federally licensed firearm manufacturer; or
  2. (II) The firearm involved has been rendered permanently inoperable; is a defaced firearm, as described in section 18-12-103; is an antique firearm, as defined in 18 U.S.C. sec. 921 (a)(16); or was manufactured before October 22, 1968.
(4)
1. (a) A person shall not knowingly sell, offer to sell, or transfer a firearm or frame or receiver of a firearm that is not imprinted with a serial number by a federal firearms licensee authorized to imprint a serial number on a firearm pursuant to federal law or subsection (7) of this section.
2. (b) This subsection (4) does not apply if:
  1. (I) The person selling, offering to sell, or transferring the firearm or frame or receiver of a firearm is a federally licensed firearm importer or federally licensed firearm manufacturer, and the person purchasing or receiving the firearm or frame or receiver of a firearm is a federally licensed firearm importer or federally licensed firearm manufacturer;
  2. (II) The firearm involved has been rendered permanently inoperable; is a defaced firearm, as described in section 18-12-103; is an antique firearm, as defined in 18 U.S.C. sec. 921 (a)(16); or was manufactured before October 22, 1968; or
  3. (III) The transfer is a temporary transfer to a federal firearms licensee for the purpose of having the firearm or frame or receiver of a firearm imprinted with a serial number pursuant to subsection (7) of this section.
(5)
1. (a)
  1. (I) A person shall not manufacture or cause to be manufactured, including through the use of a three-dimensional printer, a frame or receiver of a firearm.
  2. (II) This subsection (5)(a) does not apply to a federally licensed firearm manufacturer.
2. (b)
  1. (I) A person who owns, on the day before June 2, 2023, a firearm or a frame or receiver of a firearm that the person manufactured and that is not imprinted with a serial number by a federal firearms licensee shall, no later than January 1, 2024, have the firearm or the frame or receiver of a firearm imprinted with a serial number by a federal firearms licensee authorized to imprint a serial number on a firearm, frame, or receiver pursuant to federal law or subsection (7) of this section.
  2. (II) This subsection (5)(b) does not apply to a federal firearms licensee.
(6)
1. (a) A person who violates subsection (1), (2), (3), (4), or (5)(a) of this section commits unlawful conduct involving an unserialized firearm, frame, or receiver.
2. (b) Unlawful conduct involving an unserialized firearm, frame, or receiver is a class 1 misdemeanor; except that a second or subsequent offense is a class 5 felony.
(7)
1. (a) A federal firearms licensee may serialize a firearm or frame or receiver of a firearm, including a finished or unfinished frame or receiver, by imprinting a serial number on the firearm, frame, or receiver. To serialize a firearm, frame, or receiver, the dealer or other licensee must imprint on the firearm, frame, or receiver a serial number beginning with the dealer's or licensee's abbreviated federal firearms license number, which is the first three and last five digits of the license number, followed by a hyphen, before a unique identification number. The serial number must not be duplicated on any other firearm, frame, or receiver serialized by the licensee, and must be imprinted in a manner that complies with the requirements in federal law for imprinting a serial number on a firearm, including the minimum size and depth of the serial number and that the serial number is not susceptible to being readily obliterated, altered, or removed.
2. (b) The licensee must retain a record concerning a firearm, frame, or receiver serialized by the licensee that complies with the requirements under federal law for the sale of a firearm. In addition to any record required by federal law, a federal firearms licensee that imprints a unique serial number on a firearm, frame, or receiver pursuant to this subsection (7) shall make a record at the time of the transaction of each transaction involving serializing a firearm, frame, or receiver and keep that record. The record must include the following information: The date, name, age, and residence of any person to whom the item is transferred; and the unique serial number imprinted on the firearm, frame, or receiver. A licensee that fails to make and retain a record required in this subsection (7)(b) shall be punished as provided in section 18-12-403.
3. (c) Returning a newly serialized firearm, frame, or receiver to a person after serializing the firearm, frame, or receiver pursuant to federal law or this subsection (7) is a transfer of a firearm, and a federal firearms licensee that imprints a unique serial number on the firearm, frame, or receiver pursuant to this subsection (7) shall conduct a background check on the transferee pursuant to section 18-12-112.5 before returning the firearm to the transferee. If the transfer is denied, the licensee shall surrender the firearm, frame, or receiver to a law enforcement agency.

Source: L. 2023: Entire section added, (SB 23-279), ch. 311, p. 1894, § 2, effective June 2; (1) and (3) added, (SB 23-279), ch. 311, p. 1894, § 2, effective January 1, 2024.