Mich. Comp. Laws § 4.554

Sec. 4. The legislative files, recordings, tapes, records, memoranda, or written documents of a member of the legislature shall not be subject to a subpoena duces tecum in a civil action, contested case, or other administrative proceeding. This section shall not apply to the files, recordings, tapes, records, memoranda, or written documents of a committee, subcommittee, commission, or council of the legislature.