Mich. Comp. Laws § 750.421b

Sec. 421b. Any person who shall, without lawful authority, by force, stop or hinder the operation of any vehicle transporting farm or commercial products within this state, or the loading or unloading of such vehicle, with the intent to prevent, hinder or delay transportation, loading or unloading of such products, upon conviction thereof, shall be guilty of an offense punishable by imprisonment in the county or municipal jail for not more than 90 days or by a fine of not more than $100.00, or by both such fine and imprisonment, and upon a second or subsequent offense shall be punished by imprisonment in the state prison for not more than 2 years or by a fine of not more than $1,000.00, or by both such fine and imprisonment. This section shall not apply to railroads.