May 31, 1918 Act Repeal Act - Repeals the Act of May 31, 1918 (authorized the Secretary of the Interior to set aside and reserve a tract of land within the Fort Hall Indian Reservation, Idaho, for town-site purposes).
Gives the Shoshone-Bannock Tribes of the Fort Hall Indian Reservation the exclusive right of first refusal to purchase at fair market value any land within the Fort Hall Townsite and offered for sale.
Directs the United States to hold in trust for the benefit of the Tribes or a member of the Tribes: (1) any land they owned or acquired within the Townsite before this Act's enactment, and (2) any land they owned or acquired within the Townsite on or after this Act's enactment.
Declares that, nothing in this Act affects any valid right to any land set aside or set apart under the 1918 Act.