Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 90, § 24I

(a) As used in this section, the following words shall have the following meanings:

“Open container,” a bottle, can or other receptacle used to contain a liquid that has been opened or has a broken seal or the contents of which have been partially removed or consumed; provided, however, that a bottle resealed pursuant to section 12 of chapter 138 shall not be considered an open container; provided further, that a resealed bottle shall not be transported in the passenger area.

“Passenger area,” the area designed to seat the driver and passengers while the motor vehicle is in operation and any area that is readily accessible to the driver or a passenger while in a seated position including, but not limited to, the glove compartment; provided, however, that the passenger area shall not include a motor vehicle's trunk or a locked glove compartment or, if a motor vehicle is not equipped with a trunk, the area behind the last upright seat or an area not normally occupied by the driver or passenger.

(b) Whoever, upon any way or in any place to which the public has a right of access, or upon any way or in any place to which members of the public have access as invitees or licensees, possesses an open container of alcoholic beverage in the passenger area of any motor vehicle shall be punished by a fine of not less than $100 nor more than $500.

(c) This section shall not apply to (1) the passengers of a motor vehicle designed, maintained and used for the transportation of persons for compensation, or (2) the living quarters of a house coach or house trailer.

(d) Notwithstanding this section, the driver of any motor vehicle, including but not limited to a house coach or house trailer, shall not possess an open container of alcoholic beverage.