BEIJING - The Swiss supreme court has explained the reason it referred back Sun Yang's case, saying tweets by the president of the panel of arbitrators at the Court of Arbitration for Sport (CAS) - the Italian Franco Frattini - had exhibited possible bias against Chinese people.

The court said Sun appealed the case last April to the Swiss Federal Tribunal to annul the award rendered on Feb. 28, 2020, and submitted an application for review on the award.

The court upheld Sun's appeal as it found the tweets of Franco Frattini about animal protection issues, which had repeatedly used violent expressions, exhibited possible bias against China.

"In his tweets, the arbitrator castigates a Chinese practice of dog slaughter and denounces the consumption of this meat at a local festival in China," the Federal Supreme Court said on Friday local time.

"Some expressions refer to the skin colour of certain Chinese people he targets," it added. "In addition, the arbitrator also made the said remarks in tweets after his appointment as president of the panel of arbitrators deciding in the Sun Yang case."

"Admittedly the referee himself concedes that certain words have sometimes gone beyond his thought. To say that the words 'yellow face' are 'awkward', as the respondent foundation maintains, is however, an understatement," the court said.

It explained that even if Frattini's remarks were put in their context, "it must be admitted that the applicant's apprehensions as to the possible bias of the arbitrator in question may be regarded as objectively justified."

As a result, the request for review is allowed by the court and the award under appeal is set aside.

The case has now been sent back to CAS, which must hear it again with a different panel of judges, and the sanctions imposed on Sun were automatically lifted after the court's December decision.

The CAS had handed Sun an eight-year ban in February, 2020 after finding him guilty of refusing to cooperate with sample collectors during a visit to his Hangzhou home in September 2018.