5 U.S.C. § 4521 - Definition

(1) a law enforcement officer within the meaning of section 5541 (3) and to whom the provisions of chapter 51 apply;

(2) a member of the United States Secret Service Uniformed Division;

(3) a member of the United States Park Police;

(4) a special agent in the Diplomatic Security Service;

(5) a probation officer (referred to in section 3672 of title 18); and

(6) a pretrial services officer (referred to in section 3153 of title 18).