Legal Question in Employment Law in California

Sure, but not illegal, unless he was reporting a crime and covered under the whistle-blower doctrine. Bitching about unfair treatment or poor management does not even come close. I'm surprised they didn't fire him when he threatened to quit. In general, unless an employee is civil service, in a union, or has a written employment contract, they are an 'at will' employee that can be disciplined or fired any time for any reason, with or without �cause� or explanation, other than for illegal discrimination, harassment or retaliation under the ADA [age], Civil Rights [race, sex, ethnic, religion, pregnancy, etc], Whistle-blower, or similar statutes. The employee's goal should be to keep the employer happy.