Mich. Comp. Laws § 247.954

Sec. 4. In establishing Pure Michigan byways, the department shall consider the concept of the complete highway, which is a highway incorporating not only safety, utility, and economy but also beauty. The department shall also consider that in a complete highway pleasing appearance is a consideration in the planning and design process. The department may designate portions of a road as a Pure Michigan byway, if the department obtains a trademark license from the Michigan economic development corporation for the use of the words "Pure Michigan". Local governmental agencies shall take any action necessary to protect the integrity of a designated route as stipulated in the uniform criteria developed for the identification of Pure Michigan byways by the department.