A global sporting tribunal opened the door wider to Russian participation at the Rio Olympic Games yesterday, ruling that an Olympic ban on two Russian rowers and a swimmer with histories of doping was unenforceable.

The decision, on the eve of the opening ceremony, could invite a dozen more appeals against the ban from Russian competitors, according to the tribunal’s chief, and underlines Russian arguments that the ban lacks legal justification.

“We can do an appeal in 24 hours, so anything is possible,” Matthieu Reeb, secretary-general of the Court of Arbitration for Sport (CAS), told Reuters when asked if there was enough time for other athletes to have their ban overturned in time to compete in Rio.

In response to evidence of state-sponsored doping in Russia, the IOC last month directed sports federations to allow Russian athletes to compete only if they met certain criteria, including a clean doping past. Dozens of athletes were later excluded.

One of the athletes who could take advantage of the new ruling is whistleblower Yulia Stepanova who, together with her husband, ignited the Russian doping scandal by revealing the extent of the state-backed doping programme.

Stepanova had been cleared to compete by the world athletics federation, which praised her courage in the affair, but the IOC refused to allow her to run in Rio due to her own doping past.

The head of Russia’s Olympic committee told reporters that the ban was discriminatory.

Alexander Zhukov said it was unfair Russian sports stars such as double Olympic champion pole vaulter Yelena Isinbayeva would now watch the Games from home while past doping offenders, including top US runner Justin Gatlin, took to the field.

In its latest decision, the CAS ruled in favour of an appeal against the ban by four-times breaststroke world champion Yulia Efimova as well as rowers Anastasia Karabelshikova and Ivan Podshivalov.