Here are the materials in Chickasaw Nation v. Dept. of Interior (W.D. Okla.):
Here is the relevant statute authorizing (or mandating) the sale of the resource, as reproduced in the court’s order. Judge for yourself:
That when allotments as provided by this and other Acts of Congress have been made to all members and freedmen of the Choctaw, Chickasaw, Cherokee, Creek, and Seminole tribes, the residue of lands in each of said nations not reserved or otherwise disposed of shall be sold by the Secretary … under rules and regulations to be prescribed by him and the proceeds of such sales deposited in the United States Treasury to the credit of the respective tribes. . . . The Secretary … is hereby authorized to sell, whenever in his judgment it may be desirable, any of the unallotted land in the Choctaw and Chickasaw Nations, which is not principally valuable for mining, agricultural, or timber purposes, in tracts of not exceeding six hundred and forty acres to any one person, for a fair and reasonable price, not less than the present appraised value. . . . Provided further, That agricultural lands shall be sold in tracts of not exceeding one hundred and sixty acres to any one person.