Mich. Comp. Laws § 750.228

Sec. 228. (1) A person may lawfully own, possess, carry, or transport as a pistol a firearm greater than 26 inches in length if all of the following conditions apply: (a) The person registered the firearm as a pistol under section 2 or 2a of 1927 PA 372, MCL 28.422 and 28.422a, before January 1, 2013. (b) The person who registered the firearm as described in subdivision (a) has maintained registration of the firearm since January 1, 2013 without lapse. (c) The person possesses a copy of the license or record issued to him or her under section 2 or 2a of 1927 PA 372, MCL 28.422 and 28.422a. (2) A person who satisfies all of the conditions listed under subsection (1) nevertheless may elect to have the firearm not be considered to be a pistol. A person who makes the election under this subsection shall notify the department of state police of the election in a manner prescribed by that department.