22 C.F.R. § 92.87
Consular responsibility for serving orders to show cause
Officers of the Foreign Service are required to serve orders to show cause issued in contempt proceedings on a person who has failed or neglected to appear in answer to a subpoena served in accordance with the provisions of § 92.86. (Section 1, 62 Stat. 949; 28 U.S.C. 1784.)