Legal Question in Business Law in California

Can't imagine why......unless maybe there is some collective bargaining agreement that would apply.

Your big risk (but not your only risk) here is a potential claim by the terminated employee. The justification for laying off employees is because you don't need a certain kind of employee in a certain place. By replacing the terminated employee you are saying you did need that employee in that place.

The terminated employee(s) might bring age discrimination and/or other wrongful termination suits depending on the circumstances. If you need any more help or advice on this, please let me know.