Mass. Gen. Laws ch. 85 § 11D
Every person engaged in the retail business of selling or renting bicycles, in line skates, scooters, skate boards or other manually-propelled wheeled vehicles shall display in an area conspicuous to customers of the business a sign containing the following statement: Massachusetts law requires that a bicycle helmet be worn by a person 16 years of age or under who is riding as an operator or passenger on a bicycle, in line skates, a scooter, or a skate board.
By posting such a sign, such retail business shall be deemed to be in full compliance with this act, and no liability shall be incurred in the event that said helmet is not worn. A person, firm or corporation engaged in the business of renting bicycles shall make available a bicycle helmet conforming to the specifications for bicycle helmets of the United States Consumer Product Safety Commission to each person renting a bicycle.
Mass. Gen. Laws ch. 85, § 11D