Mass. Gen. Laws ch. 140 § 131M
No person shall sell, offer for sale, transfer or possess an assault weapon or a large capacity feeding device that was not otherwise lawfully possessed on September 13, 1994. Whoever not being licensed under the provisions of section 122 violates the provisions of 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 one year nor more than ten 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 five years nor more than 15 years, or by both such fine and imprisonment.
The provisions of this section shall not apply to: (i) the possession by a law enforcement officer; or (ii) the possession by an individual who is retired from service with a law enforcement agency and is not otherwise prohibited from receiving such a weapon or feeding device from such agency upon retirement.
Mass. Gen. Laws ch. 140, § 131M