Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 140, § 131M

(a) 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.

(b) Subsection (a) 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.

(c) Subsection (a) shall not apply to large capacity feeding devices lawfully possessed on September 13, 1994 only if such possession is: (i) on private property owned or legally controlled by the person in possession of the large capacity feeding device; (ii) on private property that is not open to the public with the express permission of the property owner or the property owner's authorized agent; (iii) while on the premises of a licensed firearms dealer or gunsmith for the purpose of lawful repair; (iv) at a licensed firing range or sports shooting competition venue; or (v) while traveling to and from these locations; provided, that the large capacity feeding device is stored unloaded and secured in a locked container in accordance with sections 131C and 131L. A person authorized under this subsection to possess a large capacity feeding device may only transfer the device to an heir or devisee, a person residing outside the commonwealth, or a licensed dealer.

(d) Whoever violates this section shall be punished, for a first offense, by a fine of not less than $1,000 nor more than $10,000 or by imprisonment for not less than 1 year nor more than 10 years, or by both such fine and imprisonment, and for a second offense, by a fine of not less than $5,000 nor more than $15,000 or by imprisonment for not less than 5 years nor more than 15 years, or by both such fine and imprisonment.

(e) This section shall not apply to transfer or possession by: (i) a qualified law enforcement officer or a qualified retired law enforcement officer, as defined in the Law Enforcement Officers Safety Act of 2004, 18 U.S.C. sections 926B and 926C, respectively, as amended; (ii) a federal, state or local law enforcement agency; or (iii) a federally licensed manufacturer solely for sale or transfer in another state or for export.