Michigan Compiled Laws, Chapter 450. Corporations § 450.1421

Sec. 421. (1) A shareholder entitled to vote at a meeting of shareholders or to express consent or dissent without a meeting may authorize other persons to act for him or her by proxy.

(2) A proxy is not valid after the expiration of 3 years from its date unless otherwise provided in the proxy.

(3) Without limiting the manner in which a shareholder may authorize another person or persons to act for him or her as proxy pursuant to subsection (1), the following methods constitute a valid means by which a shareholder may grant authority to another person to act as proxy:

(4) A copy, facsimile telecommunication, or other reliable reproduction of the writing or transmission created pursuant to subsection (3) may be substituted or used in lieu of the original writing or transmission for any purpose for which the original writing or transmission could be used, if the copy, facsimile telecommunication, or other reproduction is a complete reproduction of the entire original writing or transmission.

(5) A proxy is revocable at the pleasure of the shareholder executing it, except as otherwise provided in this section and sections 422 and 423.  1

(6) The authority of the holder of a proxy to act is not revoked by the incompetence or death of the shareholder who executed the proxy unless, before the authority is exercised, written notice of an adjudication of the incompetence or death is received by the corporate officer responsible for maintaining the list of shareholders.