Section 5. Subpoena. —

If the government employee or official, or the requested witness, who is neither the witness of the adverse party nor a hostile witness, unjustifiably declines to execute a judicial affidavit or refuses without just cause to make the relevant books, documents, or other things under his control available for copying, authentication, and eventual production in court, the requesting party may avail himself of the issuance of a subpoena ad testificandum or duces tecum under Rule 21 of the Rules of Court. The rules governing the issuance of a subpoena to the witness in this case shall be the same as when taking his deposition except that the taking of a judicial affidavit shall be understood to be ex parte.