Mich. Comp. Laws § 484.2503

Sec. 503. A person who obtains an unpublished telephone number using a telephone caller identification service shall not do any of the following without the written consent of the customer of the unpublished telephone number: (a) Disclose the unpublished telephone number to another person for commercial gain. (b) Use the unpublished telephone number to solicit business. (c) Intentionally disclose the unpublished telephone number through a computer data base, on-line bulletin board, or other similar mechanism.