Massachusetts Assault Weapons Ban

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 term "assault weapon" with "assault-style firearm" throughout the statutes. The new definition in Section 121 ^[3] broadens the scope by adding functional characteristics tests while retaining the named model list from the prior definition. Both criteria now apply.

Prohibited Items

Section 131M(a) makes it unlawful to possess, own, sell, offer for sale, or transfer:

Assault-style firearms as defined in Section 121
Untraceable firearms (ghost guns): firearms without a serial number or with an altered, removed, or obliterated serial number
Covert firearms: firearms designed or modified to not be readily recognizable as firearms (e.g., disguised as everyday objects)
Large capacity feeding devices manufactured after the applicable cutoff date

Active Constitutional Challenges

The assault weapons ban is currently subject to two active federal court challenges:

Capen v. Campbell (1st Circuit, 2025): In April 2025, the First Circuit affirmed the denial of a preliminary injunction against the Massachusetts assault weapons ban in Capen v. Campbell, 134 F.4th 660 (1st Cir. 2025), applying the historical tradition framework from Bruen.^[4] The case has returned to the district court for full adjudication on the merits, with discovery and briefing underway as of early 2026. No petition for certiorari has been filed in Capen. In June 2025, the Supreme Court declined to hear two related assault weapons ban challenges -- Snope v. Brown (Maryland) and Ocean State Tactical v. Rhode Island -- with Justice Thomas dissenting and Justices Alito and Gorsuch noting they would have granted certiorari.^[6] Justice Kavanaugh wrote separately to suggest that the Court "should and presumably will address the AR-15 issue soon, in the next Term or two." These signals from four justices are relevant context for whether the Court will grant certiorari in Capen.

Hanlon v. Campbell (D. Mass., filed August 21, 2025): An NRA-backed lawsuit brought by the NRA, Gun Owners' Action League (GOAL), Pioneer Valley Arms, and individual plaintiffs. Unlike Capen, this case challenges the constitutionality of the assault-style firearms ban under both the Second Amendment and the Fifth Amendment (vagueness). The complaint argues that an ordinary person cannot determine which firearms are prohibited under the current "assault-style" definitions.^[5] The Commonwealth's response (October 2025) asserted sovereign immunity and Eleventh Amendment defenses, advancing the theory that federal courts lack jurisdiction over Massachusetts firearms law.^[7] As of March 2026, the case is in the discovery and briefing phase with no dispositive ruling.

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. There is no mandatory minimum for Section 128 violations. 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