For the purpose of this subchapter, the term law enforcement officer means
(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).