25 USC 608 - Purchase, sale, and exchange of land

(a) Authority of Secretary; manner and place 
The Secretary of the Interior is authorized in his discretion, to
(1) purchase for the Yakima Tribes, with any funds of such tribes, and to otherwise acquire by gift, exchange, or relinquishment, any lands or interest in lands or improvements thereon within the Yakima Indian Reservation or within the area ceded to the United States by the Treaty of June 9, 1855;
(2) sell or approve sales of any tribal trust lands, any interest therein or improvements thereon, such sales being limited to agencies of the Federal, State, or local governments for recreational, educational, civic, or other public purposes, and to individual members of the tribes;
(3) exchange any tribal trust lands, including interests therein or improvements thereon, for any lands situated within such reservation or the area ceded to the United States by the treaty of June 9, 1855; and

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(b) Multiple ownership of land 
Where lands are held in multiple ownership, the Secretary is authorized to sell and exchange such lands to other Indians or the Yakima Tribes only if the sale or exchange is authorized in writing by the owners of at least a majority interest in such lands; except that no greater percentage of approval of individual Indians shall be required under sections 608 to 608c of this title than in any other statute of general application approved by Congress.
(c) Acquisitions to be held in trust 
Lands and interests in lands acquired by the Secretary pursuant to subsection (a)(1) of this section and for the benefit of the Yakima Indian Nation pursuant to section 465 of this title shall be held in trust by the United States for the benefit of the Yakima Indian Nation.
(d) Terms and conditions 
The Secretary shall obtain the advice and consent of the Yakima tribal council before entering into any of the above transactions involving the acquisition or disposition of tribal land. The terms and conditions of any such transaction, including the price at which any land is so purchased or sold and the valuation of any lands so exchanged, shall be mutually agreed upon by the Secretary, the Yakima tribal council, and the individual Indian or Indians concerned. Any such exchange of lands shall be effected on the basis of approximately equal consideration with due allowance for the value of improvements in determining the value of such lands.