Any interested party affected by a final administrative action or decision of an official of the Bureau of Indian Affairs issued under regulations in title 25 of the Code of Federal Regulations may appeal to the Board of Indian Appeals, except -
(a) To the extent that decisions which are subject to appeal to a higher official within the Bureau of Indian Affairs must first be appealed to that official;
(b) Where the decision has been approved in writing by the Secretary or Assistant Secretary - Indian Affairs prior to promulgation; or
(c) Where otherwise provided by law or regulation.