50 C.F.R. § 32.1
The opening of a wildlife refuge area to hunting will be dependent upon the provisions of law applicable to the area and upon a determination by the Secretary that the opening of the area to the hunting of migratory game birds, upland game, or big game will be compatible with the principles of sound wildlife management and will otherwise be in the public interest. The opening or closing of wildlife refuge areas to hunting shall be in accordance with the rulemaking requirements of the Administrative Procedure Act ( 5 U.S.C. 553 ). Lands acquired pursuant to the Act of May 18, 1948 (62 Stat. 238, 16 U.S.C. 695 ) will be opened to hunting only after it has been determined that the major portion of the crops in the vicinity of the area involved have been harvested, that the period of susceptibility of such crops to wildfowl depredation has passed, or that the possibility of these crops being damaged by waterfowl is minor. Lands acquired as "waterfowl production areas" shall annually be open to the hunting of migratory game birds, upland game, and big game subject to the provisions of State law and regulations and the pertinent provisions of parts 25 through 31 of this subchapter: Provided, That all forms of hunting or entry on all or any part of individual areas may be temporarily suspended by posting upon occasions of unusual or critical conditions of, or affecting land, water, vegetation, or wildlife populations.
50 C.F.R. § 32.1