According to the Washington Post —
The tribe never owned black slaves, but some individual members did. They were freed after the Civil War, in which the tribe allied with the Confederacy. An 1866 treaty between the tribe and the federal government gave the freedmen and their descendants “all the rights of native Cherokees.”
But more than 76 percent of Cherokee voters approved the amendment stripping the descendants of their citizenship. Tribal leaders who backed the amendment, including then-Principal Chief Chad Smith, said the vote was about the fundamental right of every government to determine its citizens, not about racial exclusion.
The freedmen’s descendants disagree.