Mich. Comp. Laws § 450.1422: Irrevocable proxy.

Sec. 422.

A proxy which is entitled "irrevocable proxy", and which states that it is irrevocable, is irrevocable when it is held by any of the following or a nominee of any of the following:

A pledgee of or other holder of a security interest in the shares.

A person who has purchased or agreed to purchase the shares.

A creditor of the corporation who extends or continues credit to the corporation in consideration of the proxy.

A person who has contracted to perform services as a director, officer, or employee of the corporation, if a proxy is required by the contract of employment.

A person designated by or under an agreement under section 461.

A holder of any other proxy coupled with an interest.