How Much Reasoning Is Reasonable?

Brazilian law requires arbitrators to state the reasons for their respective decisions.¹ Failure to do so may result in annulment of the arbitral award.² Unsurprisingly, plaintiffs in annulment actions usually invoke 'lack of reasoning' as one of the grounds in their attempts to set aside arbitral awards.

Although this type of challenge has not gained traction in Brazilian case law, recent opinions rendered by the Sao Paulo appellate court shed some light on how much reasoning arbitrators are required to give in their awards. These precedents show that courts are unwilling to assess the adequacy of the motives given by arbitrators, which would otherwise represent an improper judicial interference with the merits of arbitration: