Me. Rev. Stat. tit. 19-A, § 1806

This chapter does not limit a grandparent's ability to file any action not governed by the provisions of this chapter with respect to a child, including but not limited to an action to establish de facto parentage of a child under section 1891, an action for guardianship of a child under Title 18‑C, Article 5 and a child protection petition under Title 22, section 4032, subsection 1, paragraph C.