We don’t think you need to add this your personnel manual but that is clearly your call. In Selch v. Columbia Management, 2012 IL App (1st) 111434 (August 29, 2012), the Illinois Appellate Court affirmed the trial court’s dismissal of the claim over retaliatory discharge.
Plaintiff investment analyst was given a formal warning after "mooning" two superiors, but was later terminated upon the opinion of their chief executive officer who felt such behavior was egregious and harmful to the company and leadership. The trial court found Plaintiff violated the employee handbook rule and regulations by behaving in disruptive, unruly, and abusive manner, and thus violated his duties as employee.
The trial court found and the Appellate Court affirmed Plaintiff was justly terminated for cause. We assume claimant may want to avoid “moonlighting” in the future.