Mich. Comp. Laws § 712A.5: Jurisdiction over juvenile after 19 years of age.

Sec. 5.

The court does not have jurisdiction over an individual after he or she attains the age of 19 years, except as provided in section 2a of this chapter. A commitment of a juvenile to a private or public institution or agency is not valid after the juvenile has reached the age beyond which the court does not have continuing jurisdiction under section 2a of this chapter. Commitments to a private or incorporated institution or agency do not divest the court of jurisdiction unless the juvenile is adopted in a manner provided by law.