Brazilian-born Portugal soccer player Deco was cleared of doping Tuesday because of faulty procedures by a Rio de Janeiro laboratory which has since been suspended from World Cup testing.
The Court of Arbitration for Sport said a settlement between Deco, the Brazilian soccer federation and FIFA annulled his one-year ban imposed last September.
"It could not be established that (Deco) has committed an anti-doping rule violation," the CAS ruling said.
The Rio lab, known as LADETEC, has been suspended by the World Anti-Doping Agency since last August.
The lab was also dropped from World Cup testing, meaning FIFA will have to fly doping samples to Lausanne for testing during the tournament.
The lab's role for the 2016 Olympics in Rio de Janeiro is also uncertain. It was previously cited for reporting a false positive for a volleyball player.
The case against Deco, who retired last year, collapsed when his samples were re-tested in Lausanne.
The 36-year-old playmaker allegedly tested positive for two banned substances in early 2013 after playing in a Rio state championship match for Fluminense.
The lab said his samples contained hydrochlorothiazide, a diuretic which can mask the presence of other drugs, and tamoxifen, which can help cope with the side effects of using steroids.
Lausanne lab director Martial Saugy recommended that WADA "investigates directly with the Rio lab on the reliability of the results," the CAS ruling said.
Saugy noted that Deco's samples arrived in Switzerland in an "unusual container" and that the "chain of custody cannot be guaranteed."
Deco played for Portugal at the 2006 and 2010 World Cups, and for European clubs sides Barcelona, Chelsea and Porto.