5 U.S.C. § 4521: Definition

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).