Legal Question in Employment Law in California

Unfortunately, it is, unless he's changing your compensation for work already performed. As long as your total compensation is legal under minimum wage and overtime/exemption laws, and is only changed prospectively, it is legal.

Protections? The employer is entitled to set and change hours, duties, titles, compensation, benefits, leaves, vacations, holidays, policies, rules, etc. just not retroactively. Employees have the 'right' to pay and employee benefits per the state wage and hour laws, and formal company policy as agreed, to be provided a 'safe' workplace to minimize risk of injury, and sometimes are entitled to certain medical/pregnancy leave rights. That's about it. There are no laws against 'unfair treatment' or poor management.