Wrongful termination and retaliatory actions against an employee are major problems in employment law. The lives of people and families hang in the balance, and the fact that certain companies take an illegal or punitive course of action is outrageous. They are not allowed to fire or punish you for certain actions that you take.
Federal laws protect you and other employees from retaliation and wrongful termination. For example, if you are asked to perform something illegal by your employer, they can't retaliate against you or fire you for refusing to do so. They also can't fire or punish you for reporting illegal activity that the company has committed.
Similarly, a company can't take punitive action against you if you participate in an investigation that relates to the company. Along these lines, if you are a whistleblower that supplies information to investigators, the company can't punish you.
If you are wrongfully terminated or retaliated against and you intend to file a lawsuit, you need to be able to provide evidence for your allegations. You need to show that you were involved in one of the protected activities outlined above. Then you need to establish the punishment and how it affected you. And then you need to link the two to prove your case: how did the punishment directly relate to the protected activity you participated in?
These cases can be very complicated, and it is best for anyone considering legal action to consult with an experienced attorney to ensure their case is handled properly.
Source: FindLaw, "Retaliation and Wrongful Termination," Accessed May 11, 2016