Mass. Gen. Laws ch. 40M § 1
Five or more public entities may participate in an organization in which the governmental units are members, and agree to effect such property and casualty insurance coverage as the governmental unit may otherwise purchase by itself.
A self-insurance group that is issued a certificate of approval by the commissioner shall not be deemed to be insurers or insurance companies and shall not be subject to the provisions of the insurance laws and regulations of this commonwealth except as otherwise provided herein.
The provision of this chapter shall not be construed to prohibit municipal electric departments from participating in a municipal electric department self-insurance trust fund establishing pursuant to chapter one hundred and sixty-four.
Mass. Gen. Laws ch. 40M, § 1