Kamila Valieva has been cleared to participate again at the Winter Olympics. 

The 15-year-old Russian skater was the subject of a Court of Arbitration for Sport hearing following a positive drugs test.

However, the CAS has ruled that the teenager won't be provisionally suspended due to the 'exceptional circumstances' of her case.

The fact that Valieva was a 'protected person' as an under-16 also meant the anti-doping rules were unclear, they added.

She has already competed at the Games, helping the Russian Olympic Committee land gold in the team competition.

She's favourite to take top honours in the individual event tomorrow.

“On the basis of the very limited facts of this case, and after consideration of the relevant legal issues, it has been determined that no provisional suspension should be imposed on the athlete due to exceptional circumstances,” the ruling read.

“The panel considered fundamental principles of fairness, proportionality, irreparable harm and the relative balance of interests as between the applicants and the athletes, who did not test positive during the Olympic Games in Beijing and are still subject to a disciplinary procedure,” the Cas statement added.

“In particular, the panel considered preventing the athlete from competing at the Olympic Games would cause her irreparable harm in these circumstances.”

The controversy surrounds a positive drug test returned by Valieva on Christmas Day last year.

It's reported her sample returned a positive test for the heart drug trimetazidine.

Among those to criticise the decision to allow Valieva compete was the USA Olympic and Paralympic Committee.

They say they are concerned about the message it sends.