Cal. Lab. Code § 4557
Where the injury is to an employee under 16 years of age and illegally employed at the time of injury, the entire compensation otherwise recoverable shall be increased fifty percent (50%), and such additional sum shall be paid by the employer at the same time and in the same manner as the normal compensation benefits.
An employer shall not be held liable for the additional compensation provided by this section if such an employee is hired pursuant to a birth certificate, automobile driver's license, or other reasonable evidence of the fact the employee is over the age of 15 years, even though such evidence of age were falsely obtained by the employee. The additional compensation provided by this section shall not exceed the maximum sum specified by Section 4553 for additional compensation payable for serious and willful misconduct on the part of an employer. This section shall not apply to the State or any of its political subdivisions or districts.
Ca. Lab. Code § 4557