In all court actions involving any rule or order of the commission, where the commission has not been made a party, the commission shall be served with a copy of all pleadings, and shall be entitled to intervene. Where the fact that the action involves a rule or order of the commission does not appear until the time of trial, the court shall immediately direct the clerk to notify the commission of the pendency of such action, and shall permit the commission to intervene in such action.
The failure to comply with the provisions of this section shall render void and of no effect any judgment in such action, where the effect of such judgment is to modify or nullify any rule or order of the commission.