California Code, Government Code - GOV § 16645.5

(a) An employer conducting business on state property pursuant to a contract or concession agreement with the state or a state agency, or a subcontractor on such a contract or agreement, shall not use state property to hold a meeting with any employees or supervisors if the purpose of the meeting is to assist, promote, or deter union organizing. This section does not apply if the state property is equally available, without charge, to the general public for holding a meeting.

(b) An employer that violates subdivision (a) shall be liable to the state for a civil penalty equal to one thousand dollars ($1,000) per employee per meeting.