Mich. Comp. Laws § 722.1206

Sec. 206. (1) Except as otherwise provided in section 204, a court of this state may not exercise its jurisdiction under this article if, at the time of the commencement of the proceeding, a child-custody proceeding has been commenced in a court of another state having jurisdiction substantially in conformity with this act, unless the proceeding has been terminated or is stayed by the court of the other state because a court of this state is a more convenient forum under section 207. (2) Except as otherwise provided in section 204, before hearing a child-custody proceeding, a court of this state shall examine the court documents and other information supplied by the parties as required by section 209. If the court determines that, at the time of the commencement of the proceeding, a child-custody proceeding has been commenced in a court in another state having jurisdiction substantially in accordance with this act, the court of this state shall stay its proceeding and communicate with the court of the other state. If the court of the state having jurisdiction substantially in accordance with this act does not determine that the court of this state is a more appropriate forum, the court of this state shall dismiss the child-custody proceeding. (3) In a proceeding to modify a child-custody determination, a court of this state shall determine whether a proceeding to enforce the child-custody determination has been commenced in another state. If a proceeding to enforce a child-custody determination has been commenced in another state, the court may do any of the following: (a) Stay the proceeding for modification pending the entry of an order of a court of the other state enforcing, staying, denying, or dismissing the proceeding for enforcement. (b) Enjoin the parties from continuing with the proceeding for enforcement. (c) Proceed with the modification under conditions it considers appropriate.