Mich. Comp. Laws § 500.3709

Sec. 3709. (1) Except as provided in this section, requirements used by a small employer carrier in determining whether to provide coverage to a small employer shall be applied uniformly among all small employers applying for coverage or receiving coverage from the small employer carrier. If a small employer carrier waives a minimum participation rule for a small employer, the carrier cannot later enforce that minimum participation rule for that small employer. (2) A small employer carrier may deny coverage to a small employer if the small employer fails to enroll enough of its employees to meet the minimum participation rules established by the carrier pursuant to sound underwriting requirements. A minimum participation rule may require a small employer to enroll a certain number or percentage of employees with the small employer carrier as a condition of coverage. A minimum participation rule is subject to the following: (a) For a small employer of 10 or fewer eligible employees, may require enrollment of up to 100% of the small employer's employees seeking health care coverage through the small employer. (b) For a small employer of 11 to 25 eligible employees, may require enrollment of up to 75% of the small employer's employees seeking health care coverage through the small employer. (c) For a small employer of 26 to 50 eligible employees, may require enrollment of up to 50% of the small employer's employees seeking health care coverage through the small employer.