An informal arbitral award has contractual and not jurisdictional effect; it may be set aside only on the exhaustive grounds laid down in Article 808-ter of the Code of Civil Procedure and cannot be challenged under Articles 827 et seq. of the Code of Civil Procedure.
A mistake relevant for the purpose of setting aside an informal arbitral award, within the meaning of Article 1428 of the Civil Code, must be substantive, essential and recognisable, and must consist in a false representation or altered perception of the factual elements caused by having deemed existing facts which did not exist and vice versa, or by having treated uncontested facts as contested; a mistake bearing on the formation of the arbitrators’ conviction through the interpretation and evaluation of the evidence gathered is not relevant.