Me. Rev. Stat. tit. 7, § 3921-A

The commissioner shall adopt rules to establish methods of identifying wolf hybrids through tattooing, the placement of a microchip under the animal's skin or any other method determined by the commissioner as adequately providing a permanent means of identification on the body of the animal. Rules adopted pursuant to this section are routine technical rules as defined in Title 5, chapter 375, subchapter 2-A. A person may not own or keep a wolf hybrid under section 3921-B, subsection 2 or under Title 12, section 12152 unless the animal has identification in compliance with the rules adopted under this section.