The State of South Dakota is authorized and permitted to erect and maintain a good substantial fence, inclosing in whole or in part Norbeck Wildlife Preserve. The State shall erect and maintain such gates in this fence as may be required by the authorized agents of the Federal Government in administering this wildlife preserve and the adjoining national forest lands, and may erect and maintain such additional inclosures as may be agreed upon with the Secretary of Agriculture. The right of the State to maintain this fence shall continue so long as Norbeck Wildlife Preserve is also given similar protection by the laws of the State of South Dakota.