Mich. Comp. Laws § 38.2110a

Sec. 110a. (1) "Tier 1" means the retirement plan available under this act to a member who first became a judge or state official before March 31, 1997 and who does not elect to become a qualified participant of Tier 2. (2) "Tier 2" means the retirement plan established pursuant to the internal revenue code that is available to qualified participants under article VII.