16 U.S.C. § 45b

The said park shall be under the exclusive control of the Secretary of the Interior, whose duty it shall be, as soon as practicable, to make and publish such reasonable rules and regulations, not inconsistent with the laws of the United States, as he may deem necessary or proper for the care, protection, management, and improvement of the same, such regulations being primarily aimed at the freest use of said park for recreation purposes by the public and for the preservation from injury or spoliation of all timber, natural curiosities, or wonders within said park and their retention in their natural condition as far as practicable, and for the preservation of said park in a state of nature so far as is consistent with the purposes of this Act. Such rules and regulations shall permit the taking of fish by hook and line from the streams or lakes in said park, but at such seasons, during such times, and in such manner as may be directed by the Secretary of the Interior. Such rules and regulations, however, shall provide against the destruction of the wild life within said park, and the Secretary of the Interior is authorized to take all such measures as shall be necessary to fully carry out the objects and purposes of this Act. Said Secretary may, in his discretion, execute leases to parcels of ground not exceeding ten acres in extent at any one place to any one person or persons or company for not to exceed twenty years, when such ground is necessary for the erection of buildings for the accommodation of visitors. Such leases or privileges may be renewed or extended at the expiration of the terms thereof: Provided , That existing leases from the Department of Agriculture may be continued, in the discretion of the Secretary of the Interior, for so long as such extension is not detrimental to the public purposes for which the park is created.