Mich. Comp. Laws § 550.1212

Sec. 212. When, under this act or the articles of incorporation or bylaws of a health care corporation or by the terms of an agreement or instrument, a health care corporation or the board of directors of the health care corporation or any committee of the board may take action after notice to any person or after lapse of a prescribed period of time, the action may be taken without notice and without lapse of the period of time, if at any time before or after the action is completed the person entitled to notice or to participate in the action to be taken or, in case of a subscriber, by his or her attorney-in-fact, submits a signed waiver of those requirements. The attorney-in-fact may not be employed by, or receive substantial income from, the health care corporation.