Me. Rev. Stat. tit. 30-A, § 452

The sheriff in each county, in person or by the sheriff's deputies, to the extent the sheriff undertakes to patrol, shall patrol those areas in the county that have no local law enforcement but may not be required by law to patrol the entire county. The county commissioners, with the sheriff's agreement, may enter into a contract with a municipality under section 107 to provide specific patrol services by the sheriff's department in return for payment for these services.