Mich. Comp. Laws § 38.1105
A member of a reciprocal retirement system who has 30 months or more of credited service acquired as a member of the system and who has attained the age but has not met the service requirements for age and service retirement shall be entitled to use his or her credited service in force previously acquired as a member of governmental unit retirement systems in meeting the service requirements of the system from which he or she retires. Beginning September 1, 2006, if the member has a break in governmental unit employment for a period longer than 20 years, his or her service rendered in the employ of the governmental units prior to his or her last break in service shall not be used in satisfying the service requirement for age and service retirement in the system from which he or she retires. Except as provided in section 6, credited service acquired in a governmental unit in which the member was previously employed shall not be used in determining the amount of his or her retirement allowance payable by the reciprocal retirement system from which he or she retires unless otherwise provided by the retirement system.
MCL 38.1105