The Secretary is authorized (1) to issue a license to any individual upon presentation to the Secretary of satisfactory evidence that such individual is competent, and is employed (or is supervised under a contractual arrangement) by an official agency or a State agency delegated authority under section 79 or 79a of this title, to perform all or specified functions involved in original inspection or reinspection functions involved in official inspection, or in the official weighing or the supervision of weighing, other than appeal weighing, of grain in the United States; (2) to authorize any competent employee of the Secretary to (A) perform all or specified original inspection, reinspection, or appeal inspection functions involved in official inspection of grain in the United States, or of United States grain in Canadian ports, (B) perform official weighing or supervision of weighing (including appeal weighing) of grain in the United States, or of United States grain in Canadian ports, (C) supervise the official inspection, official weighing, or supervision of weighing of grain in the United States and of United States grain in Canadian ports or the testing of equipment, and (D) perform monitoring activities in foreign ports with respect to grain officially inspected and officially weighed under this chapter; (3) to contract with any person or governmental agency to perform specified sampling, laboratory testing, inspection, weighing, and similar technical functions and to license competent persons to perform such functions pursuant to such contract; and (4) to contract with any competent person for the performance of monitoring activities in foreign ports with respect to grain officially inspected and officially weighed under this chapter. Except as otherwise provided in sections 79(i) and 79a(d) of this title, no person shall perform any official inspection or weighing function for purposes of this chapter unless such person holds an unsuspended and unrevoked license or authorization from the Secretary under this chapter.