Mich. Comp. Laws § 408.971

Sec. 11. (1) This act provides minimum requirements pertaining to earned sick time and shall not be construed to preempt, limit, or otherwise affect the applicability of any other law, regulation, requirement, policy, or standard, including a collective bargaining agreement, that provides for greater accrual or use of time off, whether paid or unpaid, or that extends other protections to employees. (2) This act does not do any of the following: (a) Prohibit an employer from providing more earned sick time than is required under this act. (b) Diminish any rights provided to any employee under a collective bargaining agreement. (c) Subject to section 12, preempt or override the terms of any collective bargaining agreement in effect prior to the effective date of this act. (d) Prohibit an employer from establishing a policy that permits an employee to donate unused accrued earned sick time to another employee.