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. [C31, 35, §1287-d1; C39, § 12871.1; C46, 50, 54, 58, 62, 66, 71, 73, 75, 77, 79, 81, §686.13 ] C93, §625A.13