No lands held in trust by the United States for either the Red Cliff Band or Bad River Band of the Lake Superior Chippewa Indians, or for allottees thereof, shall be acquired or included within the boundaries of the lakeshore established by this subchapter, with the following exception:

If the Indians who own more than 50 per centum of the interest in allotment number 74 GL or allotment number 135 in the Red Cliff Reservation agree to sell the allotment to the Secretary of the Interior (hereinafter referred to as the "Secretary"), the Secretary may consent to the sale on behalf of the other owners, purchase the allotment for the negotiated price and revise the boundaries of the lakeshore to include the allotment.