Terminating an employee can be a difficult and even devastating experience to the terminated worker, but it’s also not an easy decision for the manager / employer charged with the duty of retaining and discharging employees. It’s not uncommon for an employee termination to seem unfounded or irrational. For example, an employer might decide to discharge a more senior employee or a good performer while retaining another worker who has performance issues or even many unexcused absences because the latter has a closer relationship with the employer, or compensates for his deficiencies in other ways.
If the aggrieved employee is an at-will employee, this kind of seemingly unfair preferential treatment is only illegal if the reason for it is the fact that the adversely affected employee either (1) belongs to the protected category, such as gender, sexual orientation, disability, religion, ethnicity, familial status; or (2) because the employee exercised protected rights, such as complaining about workplace harassment or unsafe working environment (internally or to the outside government agencies), reporting criminal conduct, filing a workers compensation claim, participating in a union/political activity, serving on a jury, etc.
Since the at-will employment doctrine states that an employee can be terminated for any reason, no reason, or arbitrary reason, except illegal reason, terminating one employee and keeping the other because the employer likes the second employee better for his own, personal reason, assuming that no sexual favoritism is involved, generally does not violate California of Federal employment laws.