The various Divisions of the Department of Treasury are guided by State statutes, Administrative Rules, Court cases, Revenue Administrative Bureau Bulletins, Property Tax Commission Bulletins and Letter Rulings.
All the State statutes are included in the Michigan Compiled Laws. The State Legislature's web site has the
Michigan Compiled Laws and the Constitution of the State of Michigan of 1963. A statement at the top of each page in the MCL site will tell you the last public act included the Michigan Compiled Laws.