Me. Rev. Stat. tit. 15, § 1466

If a person confined in a penal institution in any other state may be a material witness in a criminal action pending in a court of record or in a grand jury investigation in this State, a judge of the court may certify that there is a criminal proceeding or investigation by a grand jury or a criminal action pending in the court, that a person who is confined in a penal institution in the other state may be a material witness in the proceeding, investigation or action and that the person's presence will be required during a specified time. The certificate must be presented to a judge of a court of record in the other state having jurisdiction over the prisoner confined, and a notice must be given to the attorney general of the state in which the prisoner is confined.