Mich. Comp. Laws § 38.1024a

Sec. 24a. The remarriage of a surviving spouse shall not render the surviving spouse ineligible to receive a survivor's retirement allowance described in section 24. A surviving spouse whose survivor's retirement allowance described in section 24 was terminated due to the surviving spouse's remarriage shall be eligible to receive that retirement allowance beginning on the first day of the month following the month in which written application for reinstatement is filed with the board, but shall not be eligible to receive the survivor's retirement allowance attributable to any month beginning before the month of reinstatement under this section.