50 C.F.R. § 29.1
We may only authorize public or private economic use of the natural resources of any national wildlife refuge, in accordance with 16 U.S.C. 715s , where we determine that the use contributes to the achievement of the national wildlife refuge purposes or the National Wildlife Refuge System mission. We may authorize economic use by appropriate permit only when we have determined the use on a national wildlife refuge to be compatible. Persons exercising economic privileges on national wildlife refuges will be subject to the applicable provisions of this subchapter and of other applicable laws and regulations governing national wildlife refuges. Permits for economic use will contain such terms and conditions that we determine to be necessary for the proper administration of the resources. Economic use in this section includes but is not limited to grazing livestock, harvesting hay and stock feed, removing timber, firewood or other natural products of the soil, removing shell, sand or gravel, cultivating areas, or engaging in operations that facilitate approved programs on national wildlife refuges.
50 C.F.R. §29.1