Mich. Comp. Laws § 691.1557: Confidentiality.

Sec. 7.

The work product and case files of a mediator or center and communications relating to the subject matter of the dispute made during the dispute resolution process by a party, mediator, or other person are confidential and not subject to disclosure in a judicial or administrative proceeding except for either of the following:

Work product, case files, or communications for which all parties to the dispute resolution process agree in writing to waive confidentiality.

Work product, case files, or communications which are used in a subsequent action between the mediator and a party to the dispute resolution process for damages arising out of the dispute resolution process.

Subsection (1) does not apply to statements, memoranda, materials, and other tangible evidence, otherwise subject to discovery, that were not prepared specifically for use in the dispute resolution process.