28 C.F.R. § 15.4 : Judicial Administration — DEPARTMENT OF JUSTICE — CERTIFICATION AND DECERTIFICATION IN CONNECTION WITH CERTAIN SUITS BASED UPON ACTS OR OMISSIONS OF FEDERAL EMPLOYEES AND OTHER PERSONS — Removal and defense of suits

(a) The United States Attorney for the district where the civil action or proceeding is brought, or any Director of the Torts Branch, Civil Division, Department of Justice, is authorized to make the statutory certification that the Federal employee was acting within the scope of his office or employment with the Federal Government at the time of the incident out of which the suit arose.
(b) The United States Attorney for the district where the civil action or proceeding is brought, or any Director of the Torts Branch, Civil Division, Department of Justice, is authorized to make the statutory certification that the covered person was acting at the time of the incident out of which the suit arose under circumstances in which Congress has provided by statute that the remedy provided by the Federal Tort Claims Act is made the exclusive remedy.
(c) A certification under this section may be withdrawn if a further evaluation of the relevant facts or the consideration of new or additional evidence calls for such action. The making, withholding, or withdrawing of certifications, and the removal and defense of, or refusal to remove or defend, such civil actions or proceedings shall be subject to the instructions and supervision of the Assistant Attorney General in charge of the Civil Division or his or her designee.

28 C.F.R. § 15.4