46 U.S.C. § 31110: Subpoenas to officers or members of crew

An officer or member of the crew of a public vessel may not be subpoenaed in a civil action under this chapter without the consent of—(1) the Secretary of the department or the head of the independent establishment having control of the vessel at the time the cause of action arose; or (2) the master or commanding officer of the vessel at the time the subpoena is issued.