Cal. Unemp. Ins. Code § 13074

Any employer or person required to withhold and transmit any amount pursuant to this division shall comply with the requirement without resort to any legal or equitable action in a court of law or equity. Any employer or person paying to the department any amount required by it to be withheld is not liable therefor to the person from whom withheld unless the amount withheld is refunded to the withholding agent.