45 CFR 681.21: Who pays the costs for a subpoena?

The party requesting a subpoena shall pay the cost of the fees and mileage of any witness subpoenaed in the amounts that would be payable to a witness in a proceeding in United States District Court. A check for witness fees and mileage shall accompany the subpoena when served, except that when a subpoena is issued on behalf of NSF, a check of fees and mileage need not accompany the subpoena.