Immunity of federal employees from suit (Westfall Act Immunity) - Osborn v. Haley, 549 U.S. 225 (2007)
The federal statute commonly known as the Westfall Act accords federal employees absolute immunity from tort claims arising out of acts undertaken in the course of their official duties, 28 U. S. C. §2679(b)(1), and empowers the Attorney General to certify that a federal employee sued for wrongful or negligent conduct "was acting within the scope of his office or employment at the time of the incident out of which the claim arose," §2679(d)(1), (2). Upon such certification, the United States is substituted as defendant in place of the employee, and the action is thereafter governed by the Federal Tort Claims Act. If the action commenced in state court, the Westfall Act calls for its removal to a federal district court, and renders the Attorney General's certification "conclusiv[e] … for purposes of removal." §2679(d)(2).
https://biotech.law.lsu.edu/cases/immunity/osborn.htm