An arbitration clause which refers to arbitration disputes relating to the interpretation or performance of the contract, in the absence of an express contrary intention, confers upon arbitral jurisdiction exclusively disputes founded on the contract itself, to the exclusion of claims having a different causa petendi, such as claims for unjust enrichment, which find in the contract merely a factual premise.
The interpretive canon laid down by Article 808-quater of the Code of Civil Procedure, according to which an arbitration agreement extends in case of doubt to all disputes arising from the relationship to which it refers, presupposes the existence of a condition of genuine interpretive uncertainty, which is not present where the literal reference to disputes concerning the performance of the contract is unambiguous.
The res judicata formed on the question of arbitral jurisdiction in relation to claims founded on the contract does not extend to the determination of whether the arbitration clause is operative in respect of claims of a different legal nature which were not raised in the proceedings in which that res judicata was formed.
Where the arbitral award is declared null and void on the ground of the arbitrators' lack of potestas decidendi over the subject-matter decided, the rescissory phase is precluded and there is no examination on the merits of the grounds of challenge relating to the decision taken on a matter falling outside the scope of what was capable of being referred to arbitration.
An internal inconsistency between different parts of the reasoning of an arbitral award constitutes a defect under Article 829, paragraph 1, No. 5, of the Code of Civil Procedure only where it prevents the reconstruction of the logical and legal reasoning underlying the decision owing to the total absence of reasoning referable to its functional model.
A declaration of partial nullity of the arbitral award extends to the parts which are inextricably connected to the portion declared null and void, such as the set-off between reciprocal assets and liabilities which includes claims determined beyond the scope of arbitral jurisdiction.
In proceedings to set aside an arbitral award on grounds of nullity, the principle of the internal consequential effect of reversal under Article 336, paragraph 1, of the Code of Civil Procedure applies, with the consequent setting aside of the part of the award relating to costs, which must be determined in light of the final outcome of the dispute.