22 C.F.R. § 92.88
With regard to the serving of subpoenas and orders to show cause referred to in §§ 92.86 and 92.87 , section 1 of the act of June 25, 1948 (sec. 1, 62 Stat. 819, 28 U.S.C. 1783 ), provides that the subpoena shall designate the time and place for appearance before the court of the United States, and shall issue to any consular officer of the United States in the foreign country. The consular officer is required to make personal service of the subpoena and any order to show cause, rule, judgment or decree on the request of the Federal court or its marshal, and to make return thereof to such court after tendering to the witness his necessary travel and attendance expenses, which will be determined by the court and sent with the subpoena. When the subpoena or order is forwarded to the officer, it is usually accompanied by instructions directing exactly how service should be made and how the return of service should be executed. These instructions should be followed carefully.
22 C.F.R. §92.88