(a) General rule
Except as provided in subsections (b) and (c), all employees of the Agency, any of whose service after December 31, 1983, is employment for the purpose of title II of the Social Security Act [42 U.S.C. 401 et seq.] and chapter 21 of title 26, shall be subject to chapter 84 of title 5.

(b) Exception for pre-1984 employees
Participants in the Central Intelligence Agency Retirement and Disability System who were participants in such system on or before December 31, 1983, and who have not had a break in service in excess of one year since that date, are not subject to chapter 84 of title 5 without regard to whether they are subject to title II of the Social Security Act [42 U.S.C. 401 et seq.].

(c) Nonapplicability of FERS to certain employees

(1) The provisions of chapter 84 of title 5 shall not apply with respect to—

(A) any individual who separates, or who has separated, from Federal Government service after having been an employee of the Agency subject to subchapter II of this chapter; and

(B) any employee of the Agency having at least 5 years of civilian service which was performed before January 1, 1987, and is creditable under subchapter II of this chapter (determined without regard to any deposit or redeposit requirement under subchapter III of chapter 83 of title 5, or under subchapter II of this chapter, or any requirement that the individual become subject to such subchapter or to subchapter II of this chapter after performing the service involved).

(2) Paragraph (1) shall not apply with respect to an individual who has elected under regulations prescribed under section 2157 of this title to become subject to chapter 84 of title 5 to the extent provided in such regulations.

(3) An individual described in paragraph (1) shall be deemed to be an individual excluded under section 8402(b)(2) of title 5.

(d) Election to become subject to FERS
An employee who is designated as a participant in the Central Intelligence Agency Retirement and Disability System after December 31, 1987, pursuant to section 2013 of this title may elect to become subject to chapter 84 of title 5. Such election—

(1) shall not be effective unless it is made during the six-month period beginning on the date on which the employee is so designated;

(2) shall take effect beginning with the first pay period beginning after the date of the election; and

(3) shall be irrevocable.

(e) Special rules
The application of the provisions of chapter 84 of title 5 to an employee referred to in subsection (a) shall be subject to the exceptions and special rules provided in this subchapter. Any provision of that chapter which is inconsistent with a special rule provided in this subchapter shall not apply to such employees.