The Court of Arbitration for Sport has upheld an appeal by the World Anti-Doping Agency to extend the suspension though, and Guerrero will now be banned for 14 months.
The footballer's ban lapsed this month, but on Monday (NZT Tuesday) the court ruled Guerrero would now serve a 14 months suspension - an "appropriate sanction in light of Mr Guerrero's degree of fault".
Guerrero was subjected to an emotional roller-coaster after testing positive following the 0-0 draw in a qualifier away to Argentina in October.
Guerrero's absence will be a big blow for Peru, who are preparing for their first World Cup finals since 1982.
Peru is in Group C with Australia, Denmark and France.
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News of extension of the ban was not well received among Peru fans. It reduced the ban in a fast-tracked appeal last December which clearing him to play at the World Cup.
The FIFA AC had considered that Mr Guerrero had been able to establish that the adverse analytical finding had been caused by the ingestion of a tea containing the prohibited substance.
Accepting Guerrero's argument that the substance was accidentally consumed in contaminated tea, Federation Internationale de Football Association reduced the ban to six months, a period which would have enabled Guerrero to play in Russia, and he was duly named in Peru's provisional squad on Sunday.
Both the Player and WADA filed appeals at the CAS.
CAS said that Guerrero bore "some fault or negligence, even if it was not significant, and that he could have taken some measures to prevent him from committing an anti-doping violation".
Guerrero had played two games for his Brazilian club Flamengo, scoring in Sunday's 3-2 defeat against Chapecoense in the Brazilian championship, between the end of his original ban and the CAS verdict on Monday. Without the three extra points, Peru would have fallen below Chile and Paraguay in the standings and out of contention. A fan said that he had been looking forward to the World Cup, but with Guerrero's ban, there was nothing to be excited about anymore.