In the absence of different provisions in the arbitration agreement or in a separate written instrument, arbitral proceedings are conducted on the basis of the principle of freedom of form; the arbitrators are accordingly not bound to observe the rules of the code of civil procedure relating to ordinary proceedings on the merits, without prejudice to compliance with the principle of due process.
In the matter of arbitration, the arbitrators may prescribe that the time-limits fixed by them for the parties shall be peremptory only where such possibility is provided for by the arbitration agreement, or by a separate written instrument or by the procedural rules drawn up by the arbitrators themselves, and in any event with a specific warning to that effect at the time when the time-limits are set; in the absence of such conditions, the declaration of forfeiture of a party for the late exercise of the faculties of raising pleas or making applications for evidence constitutes a violation of the principle of due process.
In arbitral proceedings governed by freedom of form, the plea of limitation may be validly raised in the first defence following the memorial by which the opposing party has fully specified and identified its claims, without the rules of the procedural code governing preclusions in ordinary proceedings being rigidly applied.
A complaint of nullity of the arbitral award for failure to observe rules of law in iudicando is admissible only if confined within the same limits as the complaint of violation of law which may be raised by an appeal to the Court of Cassation pursuant to art. 360 co. 1 n. 3 cod. proc. civ.; it follows that a ground of challenge whereby, by means of a challenge of the arbitral award for nullity, the assessment of the facts adduced and the evidence obtained in the course of the arbitral proceedings is contested is inadmissible, such assessment being one contractually entrusted to the institutional competence of the arbitrators.