(a) Except as permitted below, in paragraphs (b) and (c) of this section, information or material which is classified after December 1, 1978, shall be marked at the declassification no more than six years following its original classification.
(b) Original classification may be extended beyond six years only by officials with Top Secret classification authority and agency heads listed in section 1-2 of the order. This extension authority shall be used only when these officials determine that the basis for original classification will continue throughout the entire period that the classification will be in effect and only for the following reasons:
(1) The information is ``foreign government information'' as defined by the authorities in section 1.1;
(2) The information reveals intelligence sources and methods;
(3) The information pertains to communications security;
(4) The information reveals vulnerability or capability data, the unauthorized disclosure of which can reasonably be expected to render ineffective a system, installation, or project important to the national security;
(5) The information concerns plans important to the national security, the unauthorized disclosure of which reasonably can be expected to nullify the effectiveness of the plan;
(6) The information concerns specific foreign relations matters, the continued protection of which is essential to the national security;
(7) The continued protection of the information is specifically required by statute.
(c) Even when the extension of authority is exercised, the period of original classification shall not be greater than twenty years from the date of original classification, except that the original classification of ``foreign government information'' pursuant to paragraph (b)(1) of this section may be for a period of thirty years.