The short answer is, "no." An employee cannot terminate a disabled or injured employee just because their FMLA leave expires. At that point, the question becomes whether continuation of the leave beyond 12 weeks is a reasonable accommodation for a disability. In other words, if it doesn't pose an undue hardship on the employer, then the employee must be allowed sufficient time to recover and return to work, with or without further accommodations.
The FMLA (federal) and CFRA (California) are leave laws that allow an employee to take unpaid leave from a job to care for oneself, a family member who is ill, or children who are unable to take care of themselves. PFL does not change either law and is separate from both the FMLA and CFRA. PFL provides up to 6 weeks of partial pay to workers who take time off to bond with a new child or to care for a seriously ill family member.
Often times a temporarily disabled employee can take a medical leave and return to work without any restrictions. If the employee and employer meet certain criteria, the employee will be protected from retaliation or discrimination and legally entitled to return to his or her job. Other times, however, an individual's disability requires more continued attention. Under these circumstances an employee may be entitled to a reasonable accommodation.
California provides broad protection to employees who are disabled. Sometimes an individual's disability necessitates a temporary leave of absence. If the employee and employer meet certain criteria, the employer is not permitted to fire the employee while he or she is on a disability leave.
The short answer is no, but employers frequently get this wrong. Many large corporations have policies that require termination of employees after their twelve weeks of leave is over, but the employee still needs more time to heal before returning to work. Illegal application by employers of set leave limit policies can result in a wrongful termination.