Subject to valid existing rights, the lands and interests in lands which comprise section 1-A of the Blue Ridge Parkway and lie between the southern boundary of the Shenandoah National Park at Jarman Gap and parkway centerline station 448+00 at Rockfish Gap are excluded from the parkway, made a part of the Shenandoah National Park, and shall be administered in accordance with the Act of August 25, 1916 (39 Stat. 535; 16 U.S.C. 1-4),¹ as amended and supplemented.