Check Table 1 of The Bluebook for the jurisdiction at issue. Each state has a chronological session law compilation, equivalent to the federal Statutes at Large.
A glance at T1 will show that the official compilation of Massachusetts session laws is called The Acts & Resolves of Massachusetts. Lexis and West each publish unofficial versions that are more up-to-date and may include laws not yet printed in the Acts & Resolves.
Cite according to Bluebook Rule 12.4 and T1.
Example: Regulation of Business Practice and Consumer Protection Act, 1967 Mass. Acts 781.
Note: for acts passed too recently to be included in the official session law compilation for the jurisdiction, look at the unofficial publications listed in T1.