(CNN) Doping bans on 28 Russian athletes were overturned on Thursday, throwing the International Olympic Committee's policy on Russian doping into chaos just over a week before the start of the Winter Olympics in South Korea.

The Swiss-based Court of Arbitration for Sport (CAS) upheld the appeals of athletes given lifetime Olympic bans for doping violations during the 2014 Sochi Winter Games, saying there was insufficient evidence to show they had broken the rules.

The ruling means that athletes' 2014 results are reinstated and they could now seek to participate in the Winter Games in Pyeongchang, which open on February 9.

Russian cross-country skiing star Alexander Legkov , who won gold at Sochi 2014, is among those whose bans were lifted.

In a further 11 cases, CAS ruled that doping violations had been committed but that lifetime bans were not justified and the punishments were cut to a ban for the 2018 Games alone.

The IOC said the decision "may have a serious impact on the future fight against doping," and added that it could yet appeal the decision at the Swiss Federal Tribunal, the country's highest court.

Among the reinstated athletes were cross-country skiing gold medalist Alexander Legkov, men's skeleton gold medalist Alexander Tretiakov and women's skeleton world champion Elena Nikitina.

Aleksandr Zubkov, the double Olympic bobsled champion and Russian flag bearer in Sochi, is among the 11 whose doping bans were upheld.

Russia's Alexander Tretiakov won a gold medal in the men's skeleton. It was not immediately clear if any of the 28 would seek to take part in Pyeonchang. To be eligible to compete in South Korea, they would need to be cleared by the IOC Invitation Review Panel and subsequently selected to join the team of 169 Russian athletes competing as neutrals,. The IOC banned the entire Russian team from the 2018 Games for a "systemic manipulation" of anti-doping rules. Russia denies the charge.

The Kremlin said it was "very happy" with the decision. "This information about the CAS decision regarding our athletes confirms that active efforts to protect their rights in courts and in other ways are justified, they can be effective and they must continue," Kremlin spokesman Dmitry Peskov said on a conference call with journalists