If the action challenges the legality, validity or constitutionality of a proposed constitutional amendment, the appellant shall file a written argument with the supreme court within ten days after the filing of the abstract and appellee shall file an argument within ten days thereafter, and appellant shall then file a reply within three days. The cause shall then be submitted to the supreme court in regular or special en banc session as soon thereafter as the chief justice may order.
C93, §625A.13