19 U.S.C. § 4663

Any officer or employee, while detailed or assigned under this part, shall be considered, for the purpose of preserving their allowances, privileges, rights, seniority, and other benefits as such, an officer or employee of the United States Government and of the agency of the United States Government from which detailed or assigned, and shall continue to receive compensation, allowances, and benefits from program funds appropriated to that agency or made available to that agency for purposes related to the activities of the detail or assignment, in accordance with authorities related to their employment status and agency policies.