Mich. Comp. Laws § Article IX § 18: State credit.

Sec. 18.

The credit of the state shall not be granted to, nor in aid of any person, association or corporation, public or private, except as authorized in this constitution.

This section shall not be construed to prohibit the investment of public funds until needed for current requirements or the investment of funds accumulated to provide retirement or pension benefits for public officials and employees, as provided by law.