790.12  Permit may be granted by county commissioners.--The board of county commissioners of the county, or counties, where such national forest area is located, may grant special permit for the carrying of firearms to be specifically described in such permit, when the granting of such permit shall have been recommended in writing by the officer or employee of the United States Government in charge of such national forest area; and, where such area lies in more than one county, such permit must be granted by the board of county commissioners of each of the several counties involved before the same shall be valid.