; . (B) Conforming amendment Section 8401(17)(C) of title 5, United States Code, is amended by striking (A) and (B) and inserting (A), (B), (E), and (F) . (2) Civil Service Retirement System Paragraph (20) of section 8331 of title 5, United States Code, is amended by inserting after position. (in the matter before subparagraph (A)) the following: For the purpose of this paragraph, the employees described in the preceding provision of this paragraph (in the matter before including ) shall be considered to include an employee, not otherwise covered by this paragraph, who satisfies clauses (i)–(ii) of section 8401(17)(E) and an employee of the Internal Revenue Service the duties of whose position are as described in section 8401(17)(F). . (3) Effective date Except as provided in subsection (b), the amendments made by this subsection shall take effect on the date of the enactment of this Act, and shall apply only in the case of any individual first appointed (or seeking to be first appointed) as a law enforcement officer (within the meaning of those amendments) on or after such date. (b) Treatment of service performed by incumbents (1) Law enforcement officer and service described (A) Law enforcement officer Any reference to a law enforcement officer described in this paragraph refers to an individual who satisfies the requirements of section 8331(20) or 8401(17) of title 5, United States Code (relating to the definition of a law enforcement officer) by virtue of the amendments made by subsection (a). (B) Service Any reference to service described in this paragraph refers to service performed as a law enforcement officer (as described in this paragraph). (2) Incumbent defined For purposes of this subsection, the term incumbent means an individual who— (A) is first appointed as a law enforcement officer (as described in paragraph (1)) before the date of the enactment of this Act