The Court of Arbitration for Sport (Cas) pointed to age and issues around timing of the test result announcement in the reasons for its ruling.
But critics have questioned why an athlete who has failed a drugs test is being allowed to compete on the world's biggest stage.
The World Anti-Doping Agency (Wada) said it was "disappointed" by the ruling, saying it "appears that the Cas panel decided not to apply the terms of the Code, which does not allow for specific exceptions to be made in relation to mandatory provisional suspensions for 'protected persons', including minors."
Valieva, who returned a positive test for angina-prevention drug trimetazidine on 25 December last year, had been provisionally suspended on 8 February but challenged the decision and the Russian Anti-Doping Agency (Rusada) lifted the ban the next day.
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