Rocky Mountain National Park shall be under the executive control of the Secretary of the Interior, and it shall be the duty of the said executive authority, as soon as practicable, to make and publish such reasonable rules and regulations, not inconsistent with the laws of the United States, as the said authority may deem necessary or proper for the care, protection, management, and improvement of the same, the said regulations being primarily aimed at the freest use of the said park for recreation purposes by the public and for the preservation of the natural conditions and scenic beauties thereof. The said authority may, in his discretion, execute leases to parcels of ground not exceeding twenty acres in extent in any one place to any person or company for not to exceed twenty years whenever such ground is necessary for the erection of establishments for the accommodation of visitors, may grant such other necessary privileges and concessions as he deems wise for the accommodation of visitors, and may likewise arrange for the removal of such mature or dead or down timber as he may deem necessary and advisable for the protection and improvement of the park. The regulations governing the park shall include provisions for the use of automobiles therein:  The Secretary of the Interior is authorized to accept patented lands or rights of way over patented lands in the Rocky Mountain National Park that may be donated for park purposes.
16 U.S. Code § 195 - Control; regulations; leases; sale and removal of timber
 So in original.
Section, with the exception of the last sentence, was from section 4 of act Jan. 26, 1915.
The last sentence was from section 1 of act June 12, 1917.
1919—Act Mar. 1, 1919, ch. 88, struck out “Provided, That no appropriation for the maintenance, supervision, or improvement of said park in excess of $10,000 annually shall be made unless the same shall have first been expressly authorized by law” after “automobiles therein:”.
The following state regulations pages link to this page.