Mich. Comp. Laws § 750.414a

Sec. 414a. (a) Except as provided in subsection (c) of this section, no person shall have a motor vehicle master key in his possession. (b) As used in this section, "motor vehicle master key" means a key which is designed to open locks on more than one motor vehicle but excludes keys supplied with the motor vehicle by the manufacturer or dealer or the exact duplicate of such keys, and excludes keys supplied with replacement locks or the exact duplicate of such keys. (c) The provisions of subsection (a) shall not apply to the following: (1) Keys in the possession of garage mechanics, parking lot attendants or others engaged in the business of repairing or storing motor vehicles. (2) Keys in the possession of law enforcement officers. (3) Keys in the possession of locksmiths, key makers or other persons engaged in the business of making, altering, duplicating or repairing locks or keys. (d) Violation of the provisions of this section shall be a misdemeanor.