Areas where rules were in effect on April 17, 2006 that differ from the rules set forth in subpart C are considered existing special use areas, and such differing rules remain in effect to the extent allowed by subpart A, and to the extent they are consistent with Sec. 423.28. For those existing special use areas, compliance with Sec. Sec. 423.60 through 423.62 is not required until the rules applicable in those special use areas are modified or terminated.