We must sue the individual IRS agent in equity jurisdiction and the state or government may not invoke sovereign immunity or the Eleventh Amendment and substitute itself for such a party, because the injuring party was acting outside the law and the authority of the state. Here’s a cite from Poindexter v. Greenhow, 114 U.S. 270; 5
S.Ct. 903 (1885) confirming this:
“The second head of that classification is thus described: 'Another class of cases is where an individual is sued in tort for some act injurious to another in regard to person or property, to which his defense is that he has acted under the orders of the government. In these cases he is not sued as, or because he is, the officer of the government, but as an individual, and the court is not ousted of
jurisdiction because he asserts authority as such officer. To make out his defense he must show that his authority was sufficient in law to protect him.' And in illustration of this principle reference was made to Mitchell v. Harmony, 13 How. 115; Bates v. Clark, 95 U.S. 204 ; Meigs v. McClung's Lessee, 9 Cranch, 11; Wilcox v. Jackson, 13 Pet. 498; Brown v. Huger, 21 How. 315; [114 U.S. 270, 288] Grisar v. McDowell, 6 Wall. 363; and U. S.
v Lee, 106 U.S. 196 ; S. C. 1 SUP. CT. REP. 240.”