The following common law defenses are available:
(1) An official of a Commonwealth agency, or a member of the General Assembly or the judiciary may assert on his own behalf, or the Commonwealth may assert on his behalf, defenses which have heretofore been available to such officials.
(2) An employee of a Commonwealth agency, or a member of the General Assembly or of the judiciary may assert on his own behalf, or the Commonwealth may assert on his behalf, the defense that the employee was acting pursuant to a duty required by a statute or statutorily authorized regulation.
(3) An employee of a Commonwealth agency, or a member of the General Assembly or of the judiciary may assert on his own behalf, or the Commonwealth may assert on his behalf, the defense that the act was within the discretion granted to the employee by statute or statutorily authorized regulation.