Mass. Gen. Laws ch. 164, § 35

A city shall not acquire such a plant until authorized by a two thirds vote of its city council, or of a majority of the commissioners if the city government consists of a commission, passed in each of two consecutive municipal years and thereafter ratified by a majority of the voters at an annual or special city election. If such a vote is not ratified, no similar vote shall be submitted for ratification within one year thereafter.