Massachusetts Assault Weapons Ban: MGL S. 131M

Massachusetts General Laws Chapter 140, Section 131M(a) ^[1] is the primary criminal prohibition on assault-style firearms in the Commonwealth. Chapter 135 of the Acts of 2024 ^[2] restructured the former assault weapons ban, with Section 131M(a) establishing the criminal prohibition on possession, sale, and transfer, Section 128 covering dealer licensing violations, and Section 131M(b) addressing grandfathering for lawfully possessed pre-ban firearms.

New Terminology: "Assault-Style Firearm"

Chapter 135 replaced the former term "assault weapon" with "assault-style firearm" in the firearms provisions it amended. The current Section 121 definition uses feature tests, an assault-style firearm roster, a retained named-model list, and a copy-or-duplicate clause.^[3]

Prohibited Items

Chapter 135 prohibits the following items, each under its own section of Chapter 140:

Assault-style firearms as defined in Section 121, prohibited under Section 131M(a)

Untraceable firearms (ghost guns): a firearm without a serial number, or one whose serial number has been removed, altered, or obliterated, prohibited under Section 121C (not Section 131M(a))Covert and undetectable firearms: firearms not readily recognizable as firearms, or that evade metal detection, prohibited under Section 131N (not Section 131M(a))Large capacity feeding devices as defined in Section 121, prohibited under Section 131M(a), with Section 131M(c) grandfathering for devices lawfully possessed on September 13, 1994

Current Constitutional Litigation

Capen and Hanlon: The First Circuit's April 2025 Capen decision affirmed the denial of a preliminary injunction. It was not a final merits judgment. The later Hanlon case was consolidated into the lead Capen district-court docket, and that proceeding was stayed on July 9, 2026 while the Supreme Court considers related assault-weapons cases.^[10]

Recchia v. Campbell: The First Circuit affirmed dismissal of a facial challenge under controlling circuit precedent.^[8] The panel treated the magazine argument as unpreserved and undeveloped and did not decide other arguments that had not been raised. The decision therefore should not be described as resolving every possible challenge to Massachusetts restrictions.

Third Circuit disagreement: In 2026, the en banc Third Circuit reached a contrary Second Amendment result concerning New Jersey's assault-firearm and over-10-round magazine restrictions.^[9] That ruling is not binding in Massachusetts or in the First Circuit, but it documents an active disagreement among federal appellate courts.

Penalties

Violation of Section 128 (dealer licensing violations) is punishable by a fine of not less than $1,000 nor more than $10,000, by imprisonment in state prison for not more than 10 years or in a house of correction for not more than 2.5 years, or by both fine and imprisonment. That penalty applies to a licensed dealer who sells or furnishes a firearm or ammunition to an unlicensed buyer, and it carries no mandatory minimum. Section 128 separately punishes selling, renting, leasing, or transferring a firearm without a license, or acting as an unlicensed gunsmith, by imprisonment of not less than 1 year nor more than 10 years, which is a 1-year mandatory minimum. The assault-style firearms possession penalty is in Section 131M: first offense carries not less than 1 year nor more than 10 years; second offense carries not less than 5 years nor more than 15 years.

For grandfathering provisions applicable to lawfully possessed pre-ban assault-style firearms and large capacity feeding devices, see Section 131M.

MGL Chapter 140, Section 128:
Dealer Licensing Violations and the Assault-Style Firearm Framework