Mich. Comp. Laws § 780.119: Immunity of witness; arrest or service of process.

Sec. 9.

If a witness from another state comes into or passes through this state under an order directing him to attend and testify in this or another state, he shall not while in this state pursuant to the order be subject to arrest or the service of process, civil or criminal, because of any act committed prior to his arrival in this state under the order.