Mich. Comp. Laws § 803.302a

Sec. 2a. (1) On the date a county becomes a county juvenile agency under the county juvenile agency act, the county juvenile agency shall assume responsibility for all public wards for which the department had responsibility and for which the county had financial liability under section 5 immediately before the county became a county juvenile agency. (2) If the county revokes authorization for the county juvenile agency under the county juvenile agency act, the department shall assume responsibility for the public wards for which the county juvenile agency had responsibility on the effective date of revocation.