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