Russian figure skater Kamila Valieva has been given a four-year ban for doping after initially being cleared.
A Russian Anti-Doping Agency (Rusada) investigation found the teenager bore "no fault or negligence" for a failed test before the 2022 Winter Olympics, where she won team gold aged 15.
But the Court of Arbitration for Sport (Cas) has upheld an appeal by the World Anti-Doping Agency (Wada).
"The doping of children is unforgivable," Wada said in response.
News of Valieva's failed test only emerged after she had helped Russia to team gold in Beijing.
The ban has been backdated to 25 December 2021 - the date Valieva took the failed test - and the Cas panel has also ordered "the disqualification all competitive results achieved" from that date.
However, it said the power to strip Russia of the gold medal was "not within the scope of this arbitration procedure and will have to be examined by the sports organisations concerned".
Governing body the International Skating Union welcomed the Cas decision and said it will publish a full statement with regards to the implications on Tuesday.
Cas said Valieva, who is now aged 17, did not contest the presence of a banned substance and it was asked to decide what sanctions, if any, she should face.
"Ms Valieva was not able to establish, on the balance of probabilities and on the basis of the evidence before the panel, that she had not committed the Anti-Doping Rule Violation (ADRV) intentionally," it said in its ruling.
It added it had no bearing "whether the athlete is an adult or a Protected Person" referring to Valieva's age at the time of the failed test.
The Kremlin has criticised the Cas ruling as a "politicised" decision.
What happened to Valieva?
Valieva tested positive for banned heart medication trimetazidine in December 2021.
She had become an instant global star as the first female skater to land a quadruple jump at a Winter Olympics.
Russia won gold in the team figure skating event on 7 February 2022, but it was announced four days later that Valieva had failed a drugs test before the Games.
The sample had been collected on 25 December at the Russian Figure Skating Championships in St Petersburg.
Valieva received a provisional ban but that was lifted by a court and she was allowed to compete in the women's singles event. However, her performance featured a number of falls and stumbles and she left the ice in tears.
A Rusada investigation then cleared her of intentionally doping, but Wada appealed against that finding at Cas, sport's highest court.
Wada and the International Skating Union (ISU) said they were "concerned" by the decision and sought a four-year ban, and for all her results from the date of the sample collection on 25 December 2021 to be expunged.
The ISU also called on Cas to determine the final results of the team gold event in Beijing. Though Cas says that duty will now fall elsewhere, the United States, who finished in the silver medal position, are set to be awarded gold, with Japan elevated to silver and Canada receiving bronze following their fourth-place finish two years ago.
The ISU subsequently raised the minimum age for competitors in senior events from 15 to 17 to protect skaters' "physical and mental health, and emotional well-being".
'The doping of children is unforgivable' - Wada
Wada said it welcomed the decision, saying it had appealed against the earlier decision "in the interests of fairness for athletes and clean sport - and we believe that has been delivered through this decision".
Valieva's team have always insisted the failed test was the result of contaminated cutlery which had been tainted by her grandfather's heart medication.
But Wada went on to say those behind the failed tests should face justice.
"The doping of children is unforgivable," it said.
"Doctors, coaches or other support personnel who are found to have provided performance-enhancing substances to minors should face the full force of the World Anti-Doping Code. Indeed, Wada encourages governments to consider passing legislation - as some have done already - making the doping of minors a criminal offence."
Latest chapter in Russia's doping shame
Russian athletes were only allowed to compete at the Beijing Games under the neutral name of the Russian Olympic Committee (ROC).
That was after Wada banned Russia from all international sport for four years from 2019 following a doping scandal.
Cas later reduced the ban and ruled that Russian athletes could compete at the Olympics and other international events but the team could not use the Russian name, flag, or anthem.
A Wada investigation in 2016 found Russia operated a state-sponsored doping programme for four years across the "vast majority" of summer and winter Olympic sports.
Last month the International Olympic Committee announced it would allow Russian athletes to compete as neutrals at the 2024 Summer Olympic Games in Paris - though that followed a ban on Russian competitors following the invasion of Ukraine.
Travis Tygart, chief executive of the United States Anti-Doping Agency (USADA), told OceanNewsUk: "It's been a long time coming and justice delayed and certainly justice denied. There are athletes out there who will never get their moment on the podium in front of the world during the Games.
"Of course, our hearts also go out to Valieva. How does a young girl at that age get a hold of this controlled drug? You have to look at the Russia system. And here we go again, unfortunately, with them trying to hijack the Games and at the expense of a young woman."
Tygart was also critical of Wada and looking ahead to this summer's Olympics, added: "I'm afraid we're at the last thread of confidence. And here we go again, into Paris with Russia potentially tainting those Games by sending athletes who haven't been properly tested."
Wada director general Olivier Niggli said: "We are very concerned and remain very vigilant about what's going on in Russia.
"What's more of a concern, actually, to me, is the fact that the first decision rendered by a panel in Russia was so wrong. And that's what Cas has proven today. And that, you know, doesn't give a good message in terms of how serious they are treating the problem."
