A recent post on this blog discussed the noteworthy case of a Goggle software engineer's legal claim that he was the victim of political viewpoint discrimination, and specifically, got fired for expressing a minority political view.
As the previous post alluded to, California law prohibits employers from taking adverse action against an employee simply because of an employee's political positions and activities. There is no equivalent provision in the anti-discrimination laws of the federal government.
More specifically, an employer cannot punish an employee should the employee decide to run for public office, without regard to what that employee's platform or party affiliation is.
Moreover, the employer can also not use its internal policies and practices as a means of controlling an employee's political position. This rule is rather broad in that even if an employer's role "tends" to exert such control over an employee, it has run afoul of the law.
Finally, the law put a blanket prohibition on an employer's efforts to "influence" an employee's politics.
Basically, even a private employer in California has to take some reasonable steps to keep politics out of the employer's work environment. This does not, however, mean that an employee is free to say whatever he or she wants at work so long as it is "political."
As in other cases of alleged discrimination, the law does not prohibit an employer from making objective rules that govern the conduct of the workplace, so long as those rules are enforced consistently.
Still, an employee who feels he or she got singled out because of a political viewpoint may be able to allege illegal workplace discrimination via a lawsuit.