Mich. Comp. Laws § 600.8138

Sec. 8138. (1) The seventy-third-a district consists of the county of Sanilac and is a district of the first class. Under section 810a, the probate judge for the county of Sanilac shall serve as judge of the seventy-third-a district. (2) Until April 1, 2012, the seventy-third-b district consists of the county of Huron, is a district of the first class, and has 1 judge. Beginning April 1, 2012, the seventy-third-b district consists of the county of Huron and is a district of the first class. Under section 810a, a probate judge for the county of Huron shall serve as judge of the seventy-third-b district.