Beware of What You Tweet – Social Media and the Objective Test to Challenge an Arbitrator’s Impartiality

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Author: Raúl Pereira Fleury*

Independence and Impartiality
Arbitrators and Arbitral Tribunals

On December 22, 2020, the Swiss Federal Supreme Court (the “Supreme Court”) handled its decision on the case Sun Yang v. Agence Mondiale Antidopage (AMA) and Fédération Internationale de Natation (FINA).[1] In its decision, the Supreme Court decided to annul the arbitral award rendered by a Court of Arbitration for Sport (“CAS”) tribunal[2] on the ground that there were justifiable doubts regarding the impartiality of one of the arbitrators, in this case, the president of the tribunal.[3]

The case concerned the suspension of Chinese swimmer Sun Yang for eight years for refusing to cooperate with anti-doping officials who traveled to his home in September 2018 to retrieve blood and urine samples. The CAS arbitral tribunal found this lack of cooperation to violate FINA’s doping rules (the “Arbitral Award”). It was reported that Sun Yang argued with the officials and his mother ordered a security guard to break the blood-sample containers with a hammer.[4]

The decision of the Supreme Court to set aside the Arbitral Award may seem uneventful; however, it is significant not only because CAS arbitral awards are rarely annulled, either based on lack of impartiality[5] or under any other ground, with a 0.25% annulment rate,[6] but also because in the case at hand, social media played a fundamental—if not necessary—role in the Supreme Court’s decision-making process. 


According to the Supreme Court’s press release[7] on the case dated January 15, 2021, soon after the Arbitral Award was rendered, Sun Yang discovered an article posted on the internet that covered tweets made by the arbitrator in 2018 and 2019—including after his appointment—in connection with the protection of animals. In these tweets, the arbitrator criticized the Chinese practice of dog slaughter and consumption of their meat at a local festival in China, sometimes referring to the skin color of certain Chinese people he targeted.[8]

The Supreme Court found these circumstances gave rise to justifiable and objective doubts as to the president’s impartiality, falling within one of the grounds for annulment of the arbitral award, namely, article 190(2)(a) of the Swiss Private International Law Act (“PILA”), which provides that an arbitral award may be annulled “if the sole arbitrator was not properly appointed or if the arbitral tribunal was not properly constituted.”[9] Consequently, the Supreme Court annulled the Arbitral Award and remanded the case back to the CAS to render a new award with a different tribunal.[10]

In its reasoning, the Supreme Court held that arbitrators, like judges, must present enough guarantees of their independence and impartiality. However, such independence and impartiality can only be effectively challenged if objectively ascertained circumstances give rise to an appearance of bias.[11] The Supreme Court also relied on the IBA Guidelines of Conflict of Interest in International Arbitration –recognizing their utility as an instrument for the harmonization and unification of the standards applied in international arbitration– specifically guideline 2(b), which provides that an arbitrator shall decline to accept an appointment, or resign “if facts or circumstances exist, or have arisen since the appointment, which, from the point of view of a reasonable third person having knowledge of the relevant facts and circumstances, would give rise to justifiable doubts as to the arbitrator’s impartiality or independence.”[12]

The Supreme Court recognized that arbitrators are free to defend their convictions in social media; however, this does not mean that they can express everything they think in such strong terms as the arbitrator in the Sun Yang case did, without the risk of raising some fears—even unfounded—as to their impartiality. In fact, the Supreme Court recognized that, considered abstractly, the fact that the arbitrator severely criticized the consumption of dog meat during the annual Yulin festival and denounced certain Chinese nationals who, according to him, were guilty of torturing animals could not, on its own, constitute a circumstance to say that the arbitrator is biased against any Chinese national.[13]

However, the Supreme Court noted that the issue was not the cause defended by the arbitrator, but rather the extremely violent terms used by him. In particular, the terms relating to the skin color of the Chinese people the arbitrator referred to in his tweets were, to the Supreme Court, inadmissible because they had nothing to do with the animal cruelty the arbitrator was denouncing. Moreover, the Supreme Court noted that the statements were also made after he was appointed as president of an arbitral tribunal called upon to rule on an appeal lodged by a Chinese national.[14]

The Supreme Court concluded that, from the point of view of a reasonable third party, all these facts gave rise to justifiable and objective doubts regarding the impartiality of the arbitrator challenged and created an appearance of impropriety, and therefore, annulled the Arbitral Award.


Much like other institutions, arbitration is only as effective as its stakeholders make it. In this context, the requirements of the arbitrators’ independence and impartiality are at the core of international arbitration’s legitimacy.

Focusing on the impartiality requirement, it has been said that such a feature involves a state of mind primarily. Therefore, it is a subjective and more abstract concept than independence.[15] Furthermore, while different national laws and arbitration rules provide for more or less stringent impartiality standards, proving that there is an objective lack of impartiality will be, arguably, more difficult than proving a lack of independence.

The Supreme Court’s reasoning may prove that this may no longer be the case. In a 2012 blog post, Jean Kalicki foresaw how “virtual relationships” maintained in social networks, such as Facebook, LinkedIn, and Twitter might create a host of new circumstances to challenge arbitrators’ independence and impartiality, including some recommendations for arbitrators in order to avoid such challenges.[16]

The Sun Yang case goes beyond this. In this case, the circumstances that led to the annulment of the Arbitral Award were not “virtual relationships” but rather stand-alone Twitter posts made by the arbitrator, which provided a helpful and, more importantly, objective tool for the Supreme Court to reach its decision. So, the challenge for these times is not only regarding the arbitrator’s relationships on social media but also on what they post on them, especially on less professional networks such as Facebook and Twitter, where users feel freer to post more personal opinions and thoughts.

The challenge may also be taken by arbitral institutions and international organizations devoted to developing international arbitration, such as UNCITRAL and the IBA, by establishing or revamping guidelines directed to social media use to preserve and improve international arbitration’s legitimacy.

The Sun Yang case certainly sets an important precedent regarding the arbitrators’ right to free speech on social networks. We have yet to see its repercussions in the field of sports arbitration, and in international arbitration more broadly. In the meantime, arbitrators should beware of what they tweet.

[1] Bundesgericht [BGer] [Federal Supreme Court] Dec. 22, 2020, 4A_318/2020 (Switz.).

[2] World Anti-Doping Agency (WADA) v. Mr, Sun Yang and Fédération Internationale de Natation (FINA), Court of Arbitration for Sport, CAS case No. 2019/A/6148, Arbitral Award (Feb. 28, 2020).

[3] BGer, 4A_318/2020, § 7.

[4] Victor Mather, Karen Crouse and Tariq Panja, Sun Yang, Chinese Olympic Swimmer, Gets 8-Year Doping Ban, N.Y. Times (Feb. 28, 2020),

[5] Arbitration in Switzerland: The Practitioner’s Guide 277 (Manuel Arroyo ed., 2d ed. 2018); Antonio Rigozzi, Challenging Awards of the Court of Arbitration for Sport, 1 J. Int’l Disp. Settlement 217, 236-39 (2010).

[6] This statistic was directly obtained from Ms. Katy Hogg, CAS’ Communications Officer. According to Ms. Hogg, since 1984, CAS has issued 4,700 arbitral awards. During this period, 250 appeals have been filed before the Swiss Federal Tribunal. Of these, 11 were upheld and 3 were partially upheld.

[7] Press Release of the Swiss Federal Supreme Court of January 15, 2021, available at

[8] Id.

[9] BGer, 4A_318/2020, § 4.2.

[10] Id., § 8.

[11] Id., § 6.5.

[12] Int’l Bar Ass’n, IBA Guidelines of Conflict of Interest in International Arbitration, Guideline 2(b), 5 (2014).

[13] BGer, 4A_318/2020, § 7.9.

[14] Id.

[15] Blackaby Nigel et al., Establishment and Organisation of an Arbitral Tribunal, in Redfern and Hunter on International Arbitration 255 (6th ed. 2015).

[16] Jean Kalicki, Social Media and Arbitration Conflicts of Interest: A Challenge for the 21st Century, Kluwer Arb. Blog (Apr. 23, 2012),

* Raúl is a senior associate with FERRERE Abogados’ corporate and litigation groups in Asunción, Paraguay. He specializes in corporate and financial transactions, mainly on matters related to commercial contracts, distribution, licensing, and joint ventures, as well as arbitration related matters, such as drafting of arbitration clauses, issues of choice of forum and applicable law, recognition and enforcement of arbitral awards, among others. Raúl holds an LL.M. from American University Washington College of Law and a J.D. from the Catholic University of Asunción. Email: