The arbitrator’s duty to disclose potential conflicts of interest depends on the applicable law.
The arbitrator, in France, is bound by a duty of sincerity towards the parties that can be seen on two levels, in a chronological manner. First, he must reveal all and any potential conflict of interests before accepting his or her mission, so parties can make a fully aware choice. Indeed, the ignorance by one of the parties of a circumstance that would mislead a party vitiates that party’s consent to the arbitration and so invalidates it, according to article 1010 of the French Civil Code. Secondly, although the arbitrator has not been firmly chosen by the parties, he or she must still reveal any potential conflict that would come to his or her knowledge during the arbitral proceeding. It must be noted that the arbitrator is only bound to reveal what is unknown, as opposed to publicly-available information.
The French High Court and the Paris Court of Appeal hold a very strict interpretation of the criteria defining the scope of the arbitrator’s duty to disclose. For instance, in SA Auto Guadeloupe Investissements v Colombus Acquisitions Inc, the arbitrator’s challenge was upheld although he was not aware of any developments in a relationship that was questioned by one of the parties, concerning a relationship that he had disclosed at the beginning of the arbitration proceedings.
In the United States, the courts appear to be more flexible and pragmatic. The neutral arbitrator must typically only reveal substantial and significant business relationship with a party or counsel, in order to avoid any appearance of inappropriate behavior, or at the very least a reasonable impression of bias. The duty to disclose comprises thus indirect relations between the arbitrator and the parties, through their counsels or present employers. However, its scope is still limited in comparison to French arbitration.
In the case Aimcor, the Second Circuit adopted a particularly pragmatic view of the requirement of continuity of the duty to disclose during arbitral proceedings. The court ruled that the arbitrator only need reveal conflicts that he or she became aware of during the proceeding, rather than holding him or her responsible for conflicts he or she had no knowledge of.
The American system is also more pragmatic insofar as it imposes a duty to investigate upon the arbitrator in case of doubtful facts, which does not exist in France.
 Cass Civ 2, 13 avril 1972; CA Paris, 2 juillet 1992, Gazette du Palais, 1994, 2, Somm. 721.
 Cass Civ 1, December 16 2015, SA Auto Guadeloupe Investissements v Columbus Acquisitions Inc et al, 14/26279.
 Guseinov v. Burns, 145 Cal App. 4th 944, 51 Cal. Rptr. 3d 903 (2d Dist. 2006).
 Olson v. Merrill Lynch, Pierce, Fenner & Smith Inc., 51 F.3d 157 (8th Cir. 1995).
 Aimcor v. Ovalar, US CA 2nd Circ. July 9th 2007.