Federal labor law bars even non-union employers like Google from punishing an employee for communicating with fellow employees about improving working conditions. The purpose of the memo was to persuade Google to abandon certain diversity-related practices the engineer found objectionable and to convince co-workers to join his cause, or at least discuss the points he raised.
the engineer added to his memo: "Despite what the public response seems to have been, I've gotten many personal messages from fellow Googlers expressing their gratitude for bringing up these very important issues which they agree with but would never have the courage to say or defend because of our shaming culture and the possibility of being fired." The law protects that kind of "concerted activity."
Second, the engineer's memo largely is a statement of his political views as they apply to workplace policies. The memo is styled as a lament to "Google's Ideological Echo Chamber." California law prohibits employers from threatening to fire employees to get them to adopt or refrain from adopting a particular political course of action.
Third, the engineer complained in parts of his memo about company policies that he believes violate employment discrimination laws. Those policies include support programs limited by race or gender and promotional and hiring scoring policies that consider race and gender. It is unlawful for an employer to discipline an employee for challenging conduct that the employee reasonably believed to be discriminatory, even when a court later determines the conduct was not actually prohibited by the discrimination laws.