Mich. Comp. Laws § 750.394a

Sec. 394a. (1) A person who knowingly throws any object at a motor vehicle participating in a racing event or who knowingly throws or places any object on a racecourse, without authorization, while a motor vehicle is participating in a racing event is guilty of a misdemeanor, punishable by imprisonment for not more than 1 year, or by a fine of not more than $1,000.00, or both. (2) For purposes of this section, "racing event" means a motor vehicle race that is sanctioned by a nationally or internationally recognized racing organization and that is run on a privately owned and operated racecourse, and includes preparations, practices, and qualifications for the race.