10 U.S.C. § 8874

If the court allows fees to any witness in a prize cause, or fees for taking evidence out of the district in which the court sits, and there is no money subject to its order in the cause, the marshal shall pay the fees. He shall be repaid from any money deposited to the order of the court in the cause. Any amount not so repaid to the marshal shall be allowed him as witness fees paid by him in cases in which the United States is a party.