Swiss Supreme Court annuls CAS award in Sun Yang case on discovery of circumstances justifying the removal of an arbitrator


In a landmark decision issued on 22 December 2020 and published on 15 January 2021 (case 4A_318/2020), the Swiss Federal Supreme Court upheld an application requesting the revision of a Court of Arbitration for Sport (CAS) award based on the discovery of circumstances that justifies the removal of an arbitrator.


On 4 September 2018, the famous Chinese swimmer Sun Yang underwent an out-of-competition doping control ordered by the Fédération Internationale de Natation (FINA). The circumstances in which the doping control took place were disputed.

Following the opening of a disciplinary procedure, the FINA Anti-Doping Commission cleared Sun Yang, stating the documents that officials carrying out the control presented to the swimmer did not meet the applicable requirements. In addition, the notification process was deemed irregular.

As a result, the Commission declared the anti-doping control invalid and void, pointing out that the inappropriate conduct of the doping-control assistant (who had taken photographs of the athlete) constituted a valid reason for interrupting the provision of urine samples. In addition, the blood-control assistant did not provide the athlete with documentation establishing that she was qualified to take a blood sample. Finally, the doping-control officer did not clearly indicate to the swimmer that his conduct could be considered as failure to comply with the doping control.

The World Anti-Doping Agency (WADA) appealed the Commission's decision to the CAS and requested that an eight-year competition ban be ordered. On 28 February 2020, a CAS Panel, chaired by former Italian government minister Franco Frattini, found that Sun Yang had breached FINA Doping Control Rules and suspended him for eight years.

In a nutshell, the arbitrators deemed that the athlete had been lawfully notified about the doping test and that the swimmer was not justified in requesting the destruction of the container holding the blood samples, tearing the doping control form, and preventing the doping control officer from leaving the premises with the blood samples. The CAS Panel also found that the doping-control officer had made the serious consequences of Sun's actions clear to him.

Because the athlete had already breached anti-doping rules in June 2014, CAS arbitrators ruled that the athlete should be suspended for eight years instead of four.

On 15 June 2020, Sun filed an application for revision of the award with the Swiss Federal Supreme Court. In support of his application, Sun claimed that the chairman of the CAS Panel had published unacceptable comments about Chinese nationals on his Twitter account in 2018 and 2019, and argued that these comments raised legitimate doubts about the chairman's impartiality. The contentious tweets included the following terms: "those bastard sadic chinese who brutally killed dogs and cats in Yulin"; "This yellow face chinese monster smiling while torturing a small dog, deserves the worst of the hell"; "those horrible sadics are CHINESE!"; "Old yellow-face sadic trying to kill and torture a small dog".

Court ruling

The Federal Supreme Court first examined whether the discovery of the circumstances justifying the removal of an arbitrator could be accepted if filed after the expiry of the 30-day deadline for challenging an award. The court found that the application could be admitted if the applicant exercised the required diligence (i.e. attention required by the circumstances) but was unable to make the discovery during the arbitral proceedings.

The Federal Supreme Court went on to examine whether or not the swimmer had shown the attention required by the circumstances during the arbitral proceedings, and ruled that in the absence of any other circumstances indicating a risk of impartiality, the swimmer had not breached a "duty of curiosity" by failing to detect the presence of tweets published nearly ten months before the arbitrator's appointment. The decision also states that a party cannot be required to continue its internet searches or scrutinise the messages of arbitrators on social networks during arbitration proceedings.

Finally, the Federal Supreme Court examined whether the tweets in question were likely to give rise to doubts about the arbitrator's impartiality. While noting that the chairman denounced the slaughter of dogs and the consumption of this meat at a local festival in China, the Federal Supreme Court observed that the arbitrator did not hesitate to repeatedly use extremely violent terms and that several messages were published during the CAS proceedings.

Furthermore, the federal judges noted that the terms used by the chairman clearly referred to the skin color of certain Chinese individuals, which clearly had nothing to do with the denounced acts of cruelty. Whatever the context, these terms were inadmissible. Under these circumstances, the Court concluded that doubts on the impartiality of the arbitrator were objectively justified, and ruled to annul the CAS award and remove the arbitrator.


Beyond the shocking nature of the tweets, the decision of the Federal Supreme Court clarifies that an application for revision may be filed if a party discovers circumstances that would potentially justify the removal of an arbitrator even after the expiry of the deadline for challenging an award. This approach is fully consistent with the new provisions of the Swiss Private International Law Act, which entered into force on 1 January 2021.

The decision also provides some clarifications on a party's "duty of curiosity". In this respect, the Federal Supreme Court has made it clear that while parties are required to use primary search engines and consult sources in a bid to find any risk of impartiality on the part of an arbitrator, the parties cannot be expected to systematically and thoroughly scrutinise all sources relating to a given arbitrator. The decision also points out that the mere fact that information is freely accessible on the internet does not necessarily mean that a party breached his "duty of curiosity" by not finding a certain piece of information.

In this respect, the circumstances of the case were decisive, but this reasoning is not surprising since Swiss case law has long held that the "duty of curiosity" imposes a burden of doing reasonable research on arbitrators immediately after their nomination.

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