50 C.F.R. § 26.22 : Wildlife and Fisheries — UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR — THE NATIONAL WILDLIFE REFUGE SYSTEM — PUBLIC ENTRY AND USE — PUBLIC ENTRY — General exception for entry

(a) Any person entering or using any national wildlife refuge will comply with the regulations in this subchapter C, the provisions of any special regulations and any other official notification as is appropriate under §25.31.
(b) A permit shall be required for any person entering a national wildlife refuge, unless otherwise provided under the provisions of subchapter C. The permittee will abide by all the terms and conditions set forth in the permit.

50 C.F.R. § 26.22