Montana Constitution, Article X
Section 11. Public land trust, disposition. (1) All lands of the state that have been or may be granted by congress, or acquired by gift or grant or devise from any person or corporation, shall be public lands of the state. They shall be held in trust for the people, to be disposed of as hereafter provided, for the respective purposes for which they have been or may be granted, donated or devised.
(2) No such land or any estate or interest therein shall ever be disposed of except in pursuance of general laws providing for such disposition, or until the full market value of the estate or interest disposed of, to be ascertained in such manner as may be provided by law, has been paid or safely secured to the state.
(3) No land which the state holds by grant from the United States which prescribes the manner of disposal and minimum price shall be disposed of except in the manner and for at least the price prescribed without the consent of the United States.
(4) All public land shall be classified by the board of land commissioners in a manner provided by law. Any public land may be exchanged for other land, public or private, which is equal in value and, as closely as possible, equal in area. 