Federally recognized tribes are eligible to place land into federal trust, where the land is held by the federal government for the benefit of the tribe. You can read an overview about the federal process of trust acquisitions on Turtle Talk, a blog on legal issues in Indian Country.
In Maine, the process of fee-to-trust acquisition begins with a state-level procedure before the federal approval. Attorney Corey Hinton and colleagues created a memo describing the state process for fee-to-trust land acquisition for the Passamaquoddy Tribe, Penobscot Nation, Houlton Band of Maliseet Indians, and Mi’kmaq Nation.
This memo is ready for distribution and sharing, with the disclaimer that it does not constitute legal advance from First Light to any individual, government, or organization.