Massachusetts General Laws Chapter 140, Section 121D[1], created by Chapter 135 of the Acts of 2024[2], regulates the use of 3D printers and CNC milling machines in connection with firearm manufacturing. It creates use restrictions and sale or transfer prohibitions, but it does not create a general equipment registry.
Key Prohibitions
- Use restriction: No person may use a 3D printer or CNC milling machine to manufacture or assemble any firearm without a valid License to Carry (LTC) under Section 131.
- Sale restriction: Unless an exemption in subsection (c) applies, no person may sell, offer to sell, or transfer to any person in the Commonwealth a 3D printer or CNC machine that has the "primary or intended function" of manufacturing firearms.
A machine "has the primary or intended function" of manufacturing firearms if it is "advertised, marketed or promoted to manufacture or assemble firearms, regardless of whether the printer or machine is otherwise described or classified as having other functions or as a general-purpose printer or machine."
Penalties
Imprisonment for not more than 1 year, or a fine of not more than $5,000 per firearm per violation, or both.
Exceptions
- Machines possessed by forensic laboratories
- Machines being delivered to law enforcement for the sole purpose of their destruction
- Machines possessed by common carriers and their authorized employees and agents while performing the regular and ordinary transport of firearms as merchandise for customers licensed to permit such transport
- Machines possessed by or sold to federally licensed manufacturers of firearms
- Property of the United States government
Related Provisions
Section 121C establishes firearm serialization requirements, including for privately made firearms.[3] Section 121B governs registration of firearms manufactured through these methods.[4] These are firearm requirements, not registration of the printer or mill itself. Section 121D(a) itself establishes the LTC prerequisite for using the equipment to manufacture or assemble a firearm. Section 131 governs issuance and scope of the LTC.
Referendum Status
Created by Chapter 135, this section would be repealed if the November 2026 referendum succeeds.
Verification
6 of 6 factual claims on this page were matched to their source text as of 2026-10-07.
Show the claims
| Claim | Type | Status | Source | Checked |
|---|---|---|---|---|
| MGL Chapter 140, Section 121DSource text: # § 121D 3-dimensional printers and computer numerical control milling machines; use; sale or transfer; application; violations Section 121D. (a) No person sha | STAT | verified against source | None | 2026-10-07 |
| Chapter 140, Section 121DSource text: # § 121D 3-dimensional printers and computer numerical control milling machines; use; sale or transfer; application; violations Section 121D. (a) No person sha | STAT | verified against source | None | 2026-10-07 |
| Chapter 135 of the Acts of 2024Source text: # St. 2024, c. 135: An Act Modernizing Firearm Laws ## SECTION 1. Section 172M of chapter 6 of the General Laws, as appearing in the 2022 Official Edition, is | SESSION_LAW | verified against source | None | 2026-10-07 |
| MGL Chapter 140, Section 123Source text: # § 123 Conditions of licenses Section 123. (a) As used in this section ''licensee'' shall mean a person with a license to sell under section 122. ## (b) Lic | STAT | verified against source | None | 2026-10-07 |
| MGL Chapter 140, Section 128ASource text: # § 128A Application of Sec. 131 Section 128A. (a) A person with a license to carry under section 131 may sell or transfer firearms and ammunition and a person | STAT | verified against source | None | 2026-10-07 |
| MGL Chapter 140, Section 129DSource text: # § 129D Surrender of firearms and ammunition to licensing authority upon denial of application for, or revocation of, identification card or license; right to | STAT | verified against source | None | 2026-10-07 |
Sources
Related
- MGL Chapter 140, Section 123: Dealer Licensing Requirements
- MGL Chapter 140, Section 128A: Private Firearm Transfer Provisions
- MGL Chapter 140, Section 129D: Surrender on Denial or Revocation
- MGL Chapter 140, Section 131E: Firearm Purchase Conditions (Repealed 2024)
- MGL Chapter 140, Section 131K: Approved Safety and Locking Devices
- MGL Chapter 140, Section 131P: Basic Firearms Safety Certificate