Mich. Comp. Laws § 423.17: Prohibited conduct; violation; civil fine.

Sec. 17.

A person shall not by force, intimidation, or unlawful threats compel or attempt to compel any person to do any of the following:

(a) Become or remain a member of a labor organization or otherwise affiliate with or financially support a labor organization.

(b) Refrain from joining a labor organization or otherwise affiliating with or financially supporting a labor organization.