Mich. Comp. Laws § 37.2204

Sec. 204. A labor organization shall not do any of the following: (a) Exclude or expel from membership, or otherwise discriminate against, a member or applicant for membership because of religion, race, color, national origin, age, sex, sexual orientation, gender identity or expression, height, weight, or marital status. (b) Limit, segregate, or classify membership or applicants for membership, or classify or fail or refuse to refer for employment an individual in a way that would deprive or tend to deprive that individual of an employment opportunity, or that would limit an employment opportunity, or that would adversely affect wages, hours, or employment conditions, or otherwise adversely affect the status of an employee or an applicant for employment, because of religion, race, color, national origin, age, sex, sexual orientation, gender identity or expression, height, weight, or marital status. (c) Cause or attempt to cause an employer to violate this article. (d) Fail to fairly and adequately represent a member in a grievance process because of religion, race, color, national origin, age, sex, sexual orientation, gender identity or expression, height, weight, or marital status.