Guerrero's last hope was in the Federal Court of Switzerland, where he made an appeal to have his suspension dropped, and his appeal appears to have been successful with his lawyer tweeting the CAS statement on the case confirming that the player has been made eligible to play for his country at this summer's tournament in Russian Federation.
"This decision does justice, at least partially, and I'm grateful to the Swiss court", said Guerrero, who has not formally been cleared of doping and could yet serve the remainder of his ban.
Sport's top arbitration court responded by increasing the reduced six-month ban to 14 months.
"Paolo Guerrero has also filed an urgent request for a stay of the execution of the suspension in order to be able to participate in the forthcoming FIFA World Cup in Russian Federation".
Peru take on Denmark in their first World Cup match at the Mordovia Arena in Saransk on June 16, with Guerrero now set to feature.
Just two weeks ago, the Court of Arbitration for Sport (CAS) extended Paolo Guerrero's six-month Federation Internationale de Football Association ban - which was set to expire in May - until January 2018, meaning he was going to miss the World Cup.
"There are no limits", said Peru's all-time leading scorer, who previously played for Bayern Munich.
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The verdict came four days ahead of Fifa's deadline for Peru to finalize its 23-man World Cup squad.
"Along with many professional footballers around the world, we strongly believe that Guerrero's 14-month sanction for unknowingly ingesting a banned substance is unfair and disproportionate".
Paolo Guerrero will play at the World Cup this summer.
That suspension was then halved by Fifa's appeal committee but the World Anti-Doping Agency (Wada) appealed to Cas and, less than two weeks after his six-month ban ended in May, they extended it to 14 months.
So far, the CAS panel has only issued its decision, without grounds.
Guerrero had been given a boost earlier today when the CAS said they would not object if the Tribunal ruled he is eligible to play.
CAS decided not to contest Guerrero's final appeal.