Persons employed or supervised under a contractual arrangement by an official agency (including persons employed or supervised under a contractual arrangement by a State agency under a delegation of authority pursuant to this chapter) and persons performing official inspection functions under contract with the Secretary shall not, unless otherwise employed by the Federal Government, be determined to be employees of the Federal Government of the United States: Provided, That such persons shall be considered in the performance of any official inspection, official weighing, or supervision of weighing function as prescribed by this chapter or by the rules and regulations of the Secretary, as persons acting for or on behalf of the United States, for the purpose of determining the application of section
201 of title
18, to such persons and as employees of the Department of Agriculture assigned to perform inspection functions for the purposes of sections
1114 and
111 of title
18.