Action to annul an administrative decision of the president of an arbitration institution which, in applying the institutional rules, appoints all members of the arbitral tribunal and removes a co-arbitrator whose nomination had already been accepted. Possibility of judicial review, since it is an administrative (and not jurisdictional) act that is unappealable within the arbitration institution. Violation of the party's right to appoint a co-arbitrator (article 13 of the Brazilian Arbitration Act). Annulment of the decision: