45 C.F.R. § 2.4 : Public Welfare — DEPARTMENT OF HEALTH AND HUMAN SERVICES — GENERAL ADMINISTRATION — TESTIMONY BY EMPLOYEES AND PRODUCTION OF DOCUMENTS IN PROCEEDINGS WHERE THE UNITED STATES IS NOT A PARTY — Procedures when voluntary testimony is requested or when an employee is subpoenaed

(a) All requests for testimony by an employee or former employee of the DHHS in his or her official capacity and not subject to the exceptions set forth in §2.1(d) of this part must be addressed to the Agency head in writing and must state the nature of the requested testimony, why the information sought is unavailable by any other means, and the reasons why the testimony would be in the interest of the DHHS or the federal government.
(b) If the Agency head denies approval to comply with a subpoena for testimony, or if the Agency head has not acted by the return date, the employee will be directed to appear at the stated time and place, unless advised by the Office of the General Counsel that responding to the subpoena would be inappropriate (in such circumstances as, for example, an instance where the subpoena was not validly issued or served, where the subpoena has been withdrawn, or where discovery has been stayed), produce a copy of these regulations, and respectfully decline to testify or produce any documents on the basis of these regulations.

45 C.F.R. § 2.4

68 FR 25840, 5/14/2003