Mich. Comp. Laws § 333.18237
A psychologist licensed or allowed to use that title under this part or an individual under his or her supervision cannot be compelled to disclose confidential information acquired from an individual consulting the psychologist in his or her professional capacity if the information is necessary to enable the psychologist to render services. Information may be disclosed with the consent of the individual consulting the psychologist, or if the individual consulting the psychologist is a minor, with the consent of the minor's guardian, pursuant to section 16222 if the psychologist reasonably believes it is necessary to disclose the information to comply with section 16222, or under section 16281. In a contest on the admission of a deceased individual's will to probate, an heir at law of the decedent, whether a proponent or contestant of the will, and the personal representative of the decedent may waive the privilege created by this section.
MCL 333.18237