In any legal proceeding before the Department or in which the United States (including any federal agency or officer of the United States) is a party:
(a) Agency counsel shall arrange for an employee to testify as a witness for the United States whenever the attorney representing the United States requests it.
(b) An employee may testify for the United States both as to facts within the employee's personal knowledge and as an expert or opinion witness. Except as provided in paragraph (c) of this section, an employee may not testify as an expert or opinion witness, with regard to any matter arising out of the employee's official duties or the functions of the Department, for any party other than the United States in any legal proceeding in which the United States is a party. An employee who receives a demand to testify on behalf of a party other than the United States may testify as to facts within the employee's personal knowledge, provided that the testimony be subject to the prior approval of agency counsel and to the Federal Rules of Civil Procedure and any applicable claims of privilege.
(c) An employee may testify as an expert or opinion witness on behalf of an officer or enlisted member of the Coast Guard in any legal proceeding conducted by the Coast Guard.