The vis attractiva of the arbitration clause operates in respect of all disputes which have their own causa petendi in the contract containing said clause, with the exclusion of those which have in the contract merely an historical presupposition. The principle of favor arbitrati pursuant to Article 808-quater of the Code of Civil Procedure requires that all claims having their causa petendi in the contract itself fall within arbitral jurisdiction.
Optional joinder pursuant to Article 103 of the Code of Civil Procedure does not impede the operativeness of the arbitration clause. Any cumulation of claims deriving from connected facts does not impose a unitary decision when there does not subsist a connection such as to require the necessary participation of all parties to the substantive relationship.
Article 819-quater, paragraph 3, of the Code of Civil Procedure, which disciplines multilateral arbitration, applies exclusively when all parties involved in the proceedings are parties to the same contract containing the arbitral clause. The provision does not operate when one of the defendants is not party to the arbitral agreement.