When St. 2024, c. 135 took effect on October 2, 2024, it dramatically expanded the Massachusetts ban on assault-style firearms and on the transfer of large capacity feeding devices. It did not, however, sweep in everything that had been lawfully owned the day before. The Legislature wrote two narrow grandfather provisions into G.L. c. 140, § 131M. One protects assault-style firearms lawfully possessed on August 1, 2024. The other protects large capacity feeding devices lawfully possessed on September 13, 1994, and only under tightly defined conditions.
Both provisions sound straightforward and are not. The protection depends on documentary proof of date of acquisition, on continued compliance with registration and serialization requirements, and on a transfer regime that essentially freezes the grandfathered item in place until inheritance. This post walks through each grandfather provision, what it actually requires, and the practical traps that catch even careful gun owners.
What § 131M Actually Bans
Before the grandfather discussion makes sense, the underlying ban needs to be clear. G.L. c. 140, § 131M(a), as rewritten by St. 2024, c. 135, provides: "No person shall possess, own, offer for sale, sell or otherwise transfer in the commonwealth or import into the commonwealth an assault-style firearm, or a large capacity feeding device."
That is a flat prohibition on possession, not just on transfer. Possession alone is the criminal act. The penalties under § 131M(d) are severe: for a first offense, a fine of $1,000 to $10,000, imprisonment of one to ten years, or both. For a second offense, $5,000 to $15,000 and five to fifteen years.
The grandfather provisions are exceptions to that flat ban, and the Legislature drafted them narrowly.
Assault-Style Firearm Grandfathering: § 131M(b)
Section 131M(b) provides that the possession ban "shall not apply to an assault-style firearm lawfully possessed within the commonwealth on August 1, 2024, by an owner in possession of a license to carry issued under section 131 or by a holder of a license to sell under section 122; provided, that the assault-style firearm shall be registered in accordance with section 121B and serialized in accordance with section 121C."
Read it carefully. The grandfather requires four things, all of which must be true.
One: lawful possession on August 1, 2024. Not lawful purchase. Not lawful order placement. Lawful possession. The firearm had to be physically in your possession or under your control on or before August 1, 2024, in compliance with the law as it stood that day. Items ordered before that date but delivered after are not grandfathered. Items in transit are not grandfathered. Items in storage at a dealer pending pickup are at best ambiguous and likely not grandfathered.
Two: lawful possession on August 1, 2024. The same date language carries a separate weight. The firearm must have been lawful under the version of § 131M then in effect (the pre-amendment version, which applied to a narrower assault-weapons category), and the owner must have been in compliance with all applicable registration and licensing rules. If the firearm was contraband on August 1, 2024 (for instance, an unregistered private build that should have been serialized), the grandfather does not retroactively cure that.
Three: LTC or dealer license held by the owner. A holder of an FID alone does not qualify. The owner must have either a license to carry under § 131 or a license to sell under § 122. The grandfather is keyed to the LTC/dealer category specifically.
Four: registered under § 121B and serialized under § 121C. This is the operational condition. Even if the firearm was lawfully possessed on August 1, 2024, the grandfather lapses if the firearm is not registered in the electronic firearms registration system and properly serialized to the standards in § 121C (a unique serial number engraved, cast, or permanently embedded to a depth of at least .003 inches in print at least 1/16 inch).
If any of those four elements is missing, the grandfather does not apply and possession is a § 131M violation.
What § 131M(b) does not provide is a transfer mechanism. The text grandfathers the owner's possession of the firearm. It does not authorize the owner to sell or transfer the firearm to anyone within the Commonwealth other than under exceptions outlined elsewhere in the chapter. As a practical matter, the grandfathered AsF is locked to the original lawful owner for the rest of that owner's life.
Large Capacity Feeding Device Grandfathering: § 131M(c)
The LCM grandfather is older and tighter. It traces to the original 1994 federal Assault Weapons Ban and was preserved through the Massachusetts permanent ban. Section 131M(c) provides that the possession ban "shall not apply to large capacity feeding devices lawfully possessed on September 13, 1994 only if such possession is" within five enumerated locations.
Read that "only if" clause literally. The grandfather is conditioned not just on lawful possession as of September 13, 1994 (a date now over thirty years in the past) but also on use only in specific places:
(i) on private property the possessor owns or legally controls; (ii) on private property not open to the public, with the owner's express permission; (iii) at a licensed dealer or gunsmith for lawful repair; (iv) at a licensed firing range or sports shooting competition venue; or (v) traveling to and from those locations, provided the LCM is unloaded and stored in a locked container per §§ 131C and 131L.
Anywhere else is unlawful possession. Carrying a grandfathered LCM in a glove compartment to lunch is not within the exception. Bringing it to a friend's house that is open to the public (a backyard cookout where strangers might attend) is not within the exception. Possession outside the enumerated locations is a § 131M offense regardless of the 1994 grandfather.
The transfer rule is even tighter. The same subsection limits transfer of a grandfathered LCM to: (a) an heir or devisee; (b) a person residing outside the Commonwealth; or (c) a licensed dealer. There is no path to sell the LCM to another Massachusetts citizen. The grandfather essentially freezes the device until inheritance or out-of-state transfer.
The Documentary Proof Problem
Both grandfather provisions are date-anchored. The legal protection turns on the precise date of lawful possession. The proof burden in any prosecution turns on whether the owner can establish that date.
For LCMs, "lawfully possessed on September 13, 1994" is a date that was over three decades ago when this post is being written. Most LCMs in private hands carry no purchase documentation tying them to that date. Receipts from the early 1990s have long been discarded. Box-stock factory magazines were not individually serialized. The owner who claims grandfather protection in 2026 needs evidence and rarely has it.
Two practical proof approaches help. The first is to identify the firearm itself as one that would have shipped from the factory with a high-capacity magazine before 1994 (e.g., a 1990s-vintage Beretta 92F shipped with a 15-round magazine) and to maintain ownership documentation for the firearm with the magazine. The second is to maintain an estate-style chain of custody (an aunt's husband's collection inherited in 2003 with documented receipts back to the original purchase). Neither is a perfect defense, but both are far better than an unadorned "I've had it forever" statement.
For assault-style firearms, the August 1, 2024 date is more recent and the proof problem is correspondingly easier. Most owners can produce dealer receipts, registration confirmations from the electronic firearms system, or the original 4473 federal transfer form. But the proof burden still falls on the owner. If the firearm was acquired through a private transfer that did not generate documentation, the grandfather defense is weaker.
What Happens at Death
The transfer rules built into the grandfather provisions create a meaningful inheritance issue. A grandfathered AsF or LCM passes through an estate to heirs or devisees, but the inherited item carries the same restrictions: the new owner must maintain registration and serialization, must hold the appropriate license, and must use the LCM only in the enumerated locations.
The inheritance window is § 129C(a)(iii): heirs or devisees may possess the firearm or ammunition for up to 60 days after transfer into their possession, during which time they must either obtain proper licensure (and meet the grandfather conditions) or transfer the item to a duly licensed person under § 128A. If the heir cannot lawfully take the item, surrender to the Colonel under § 131O is the clean exit.
The 60-day window matters. Heirs often discover firearms during estate cleanup weeks after the death and assume they have unlimited time to sort out the legal status. They do not.
The Referendum Wildcard
St. 2024, c. 135 is subject to a veto referendum certified for the November 3, 2026 ballot. If the referendum passes, the entire act is repealed and the prior version of § 131M (and the prior, narrower assault-weapon definitions) returns. If the referendum fails, the act stays in effect.
What the referendum result means for grandfathered items is not entirely clear and depends on which prior version of § 131M is the rebound point. The most likely outcome is that the older 2016 framework (which itself contained a "copy or duplicate" definition with its own July 20, 2016 grandfather) becomes operative again. Anyone holding a grandfathered AsF or LCM should plan for both contingencies and track the referendum closely.
Practical Compliance Checklist
For owners holding what may be grandfathered items, a short pre-compliance audit is worth doing now:
Documentary proof. Locate and preserve the original purchase documentation, federal Form 4473 if applicable, MA registration confirmation, and any photographs or correspondence showing the item was in your possession on or before the relevant grandfather date. Store copies separately from the firearm itself.
Registration verification. Pull a current copy of your registration entries from the electronic firearms registration system. Confirm each grandfathered item is registered to you and the description matches the physical firearm or device.
Serial number condition. Inspect the serial number on each AsF for legibility. A worn or partially obliterated serial number is itself a § 11C offense and will eliminate the grandfather defense even if all other conditions are met.
License currency. Confirm your LTC or dealer license is current and unrestricted. The grandfather is conditioned on license possession; an expired or suspended LTC eliminates the protection during the period of suspension.
Storage compliance. Confirm storage practices comply with §§ 131C and 131L. The LCM grandfather in particular requires unloaded-and-locked storage during transit; a violation of that storage rule independently breaks the grandfather.
Estate planning. If you intend grandfathered items to pass to heirs, document the heirs' eligibility (LTC status, willingness to comply with the conditions), and address the items specifically in the will or trust. The 60-day post-death window is short.
The Bottom Line
Massachusetts grandfathering under St. 2024, c. 135 is real but narrow. The AsF grandfather requires lawful pre-August-1-2024 possession, an LTC or dealer license, current registration, and proper serialization, all of which must be true simultaneously. The LCM grandfather requires pre-September-13-1994 possession plus continuing limited use in five enumerated locations, with transfer essentially impossible inside Massachusetts.
The grandfather protections are also conditioned on documentation the owner usually does not have or has not preserved. For the AsF grandfather, the proof problem is manageable. For the LCM grandfather, it is genuinely difficult. Anyone planning to assert either grandfather defense should assemble the proof package now, while documents and witnesses are still available, rather than after a charging decision has been made.
If you have questions about whether a specific firearm or feeding device qualifies for grandfather protection, or about how to handle inherited items that may fall within these provisions, contact my office.