Former Portugal midfielder Deco has been cleared of doping because of faulty testing by a Rio de Janeiro laboratory that has since been suspended from World Cup duty.
The Court of Arbitration for Sport (CAS) said on Tuesday that a settlement between Deco, the Brazilian football federation and FIFA annulled his one-year ban, which was imposed last September.
"It could not be established that (Deco) has committed an anti-doping rule violation," the published ruling from CAS said.
The lab, known as LADETEC, is further discredited after being suspended by the World Anti-Doping Agency last August. It was then dropped from the World Cup testing program, forcing FIFA to organise and pay for flying players' samples to Lausanne.
The lab's intended role in the 2016 Rio de Janeiro Olympics is also unclear because of its competence issues. It was previously exposed for mistakenly labelling a volleyball player as a doper.
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 that 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 "first that WADA investigates directly with the Rio lab on the reliability of the results," the court ruling said.
Saugy noted that Deco's samples arrived in Switzerland in an "unusual container" and that the "chain of custody cannot be guaranteed."
Former Porto, Barcelona and Chelsea star Deco played for Portugal at the 2006 and 2010 World Cups. He retired in August last year.