Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 175, § 111D

A policy of motor vehicle liability insurance issued under subdivision (b) of clause Sixth of section forty-seven, or an endorsement or rider attached thereto, may provide for the payment of all sums which the insured or his legal representative shall be legally entitled to recover as damages from the owner or operator of an uninsured motor vehicle because of bodily injury, sickness or disease, including death resulting therefrom, sustained by the insured, caused by accident and arising out of the ownership, maintenance or use of such uninsured motor vehicle. Such policy or endorsement or rider shall provide that determination as to whether the insured or his legal representative is legally entitled to recover such damages, and if so the amount thereof, shall be made by agreement between the insured or such representative and the insurer or, if they fail to agree, by arbitration. The provisions of section one hundred and eight shall not apply to any such policy or endorsement or rider providing for the payment of the sums permitted by this section.