(a) A governmental act or proceeding of a district is conclusively presumed, as of the date it occurred, valid and to have occurred in accordance with all applicable statutes and rules if:
(1) the third anniversary of the effective date of the act or proceeding has expired; and
(2) a lawsuit to annul or invalidate the act or proceeding has not been filed on or before that third anniversary.
(b) This section does not apply to:
(1) an act or proceeding that was void at the time it occurred;
(2) an act or proceeding that, under a statute of this state or the United States, was a misdemeanor or felony at the time the act or proceeding occurred;
(3) a rule that, at the time it was passed, was preempted by a statute of this state or the United States, including § 1.06 or 109.57, Alcoholic Beverage Code; or
(4) a matter that on the effective date of this section:
(A) is involved in litigation if the litigation ultimately results in the matter being held invalid by a final judgment of a court; or
(B) has been held invalid by a final judgment of a court.