Mich. Comp. Laws § 257.1261

Sec. 21. Each of the following applies concerning the applicability of this act: (a) This act applies to all warranted products sold or offered for sale on or after the effective date of this act. (b) The failure of any person to comply with this act before its effective date is not admissible in any court proceeding, administrative proceeding, arbitration, or alternative dispute resolution proceeding and may not otherwise be used to prove that the action of any person or the affected warranted product is unlawful or otherwise improper. This subdivision does not limit the availability of any claim or cause of action for a violation of any other state or federal law.