Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 140, § 174F

(a) A person shall not confine an animal in a motor vehicle in a manner that could reasonably be expected to threaten the health of the animal due to exposure to extreme heat or cold.

(b) After making reasonable efforts to locate a motor vehicle's owner, an animal control officer, as defined in section 136A, law enforcement officer or fire fighter may enter a motor vehicle by any reasonable means to protect the health and safety of an animal. An animal control officer, law enforcement officer or fire fighter may enter the motor vehicle for the sole purpose of assisting the animal and may not search the vehicle or seize items found in the vehicle unless otherwise permitted by law.

(c) An animal control officer, law enforcement officer or fire fighter who removes or otherwise retrieves an animal under this section shall leave written notice in a secure and conspicuous location on or in the motor vehicle bearing the officer's or fire fighter's name and title and the address of the location where the animal may be retrieved. The owner may retrieve the animal only after payment of all charges that have accrued for the maintenance, care, medical treatment and impoundment of the animal.

(d) An animal control officer, law enforcement officer or fire fighter who removes or otherwise retrieves an animal from a motor vehicle under subsection (b), and the agency or municipality that employs the officer or fire fighter shall be immune from criminal or civil liability that might otherwise result from the removal.

(e) After making reasonable efforts to locate a motor vehicle's owner, a person other than an animal control officer, law enforcement officer or fire fighter shall not enter a motor vehicle to remove an animal to protect the health and safety of that animal in immediate danger unless the person: (i) notifies law enforcement or calls 911 before entering the vehicle; (ii) determines that the motor vehicle is locked or there is no other reasonable means for exit and uses not more force than reasonably necessary to enter the motor vehicle and remove the animal; (iii) has a good faith and reasonable belief, based upon known circumstances, that entry into the vehicle is reasonably necessary to prevent imminent danger or harm to the animal; and (iv) remains with the animal in a safe location in reasonable proximity to the vehicle until law enforcement or another first responder arrives.

(f) A person who removes an animal from a motor vehicle pursuant to subsection (e) shall be immune from criminal or civil liability that might otherwise result from the removal.

(g) A violation of subsection (a) shall be a civil infraction punishable by a fine of not more than $150 for a first offense, by a fine of not more than $300 for a second offense and by a fine of not more than $500 for a third or subsequent offense.

(h) Nothing in this section shall preclude prosecution under section 77 of chapter 272.

(i) A city or town shall enforce this section through its animal control officers or police officers in a manner consistent with the disposition provisions in section 21D of chapter 40.