As has been widely reported, Mozilla (the maker of the Firefox search engine) recently forced its CEO, Brendan Eich, to resign because he donated $1,000 in 2008 to support California's Proposition 8, which would have banned same sex marriage. (The Proposition was approved by a majority of voters but invalidated by a federal district court).
The termination has generated a hot debate. Most commentators have framed the issue, however, as how to properly strike a balance between an employee's political free speech and his employer's desire to communicate a particular corporate "culture." (see e.g., here and here).
What these commentators seem to have overlooked, however, is that the California Labor Code has already resolved this debate. Under California law it is blatantly illegal to fire an employee because he has donated money to a political campaign. This rule is clearly set forth in Labor Code sections 1101-1102:
§ 1101. Political activities of employees; prohibition of prevention or control by employer
No employer shall make, adopt, or enforce any rule, regulation, or policy:
(a) Forbidding or preventing employees from engaging or participating in politics or from becoming candidates for public office.
(b) Controlling or directing, or tending to control or direct the political activities or affiliations of employees.
§ 1102. Coercion or influence of political activities of employees
No employer shall coerce or influence or attempt to coerce or influence his employees through or by means of threat of discharge or loss of employment to adopt or follow or refrain from adopting or following any particular course or line of political action or political activity.
Donating money to a political cause is obviously the most core form of political participation. But employers and employees should also be aware that the California Supreme Court has broadly extended the scope of protected speech and conduct to include all types of advocacy. Indeed, in Gay Law Students Association v. Pac. Tel. & Tel. Co., the Court specifically held that one's espoused attitudes about homosexuality were a form of protected conduct.
[Plaintiff's] allegations can reasonably be construed as charging that PT&T discriminates in particular against persons who identify themselves as homosexual, who defend homosexuality, or who are identified with activist homosexual organizations. So construed, the allegations charge that PT&T has adopted a “policy . . . tending to control or direct the political activities or affiliations of employees” in violation of section 1101, and has “attempt(ed) to coerce or influence . . . employees . . . to . . . refrain from adopting (a) particular course or line of political . . . activity” in violation of section 1102.
As terminating an employee for "defend[ing] homosexuality" is illegal political discrimination, one would be hard pressed to come up with a principled argument that opposition to same-sex marriage is somehow not also protected.
Thus, to the extent employers want to follow in Mozilla's footsteps by policing their employees' politics in the interests of "culture," "inclusiveness," or corporate branding, they should be aware that their efforts will violate California law.