5 U.S.C. § 4521

(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 ).