Paris St Germain have won a legal battle against UEFA after European football's governing body tried to reopen their investigation into the French club's spending on transfer fees and wages.
The Court of Arbitration for Sport said on Tuesday they have upheld PSG's appeal against UEFA on the grounds that the body took too long to review their own decision to clear the French champions of breaking Financial Fair Play rules.
The judgement is separate to an ongoing investigation by UEFA regarding PSG's 2017-18 finances -- the season in which the club signed Neymar in a world record 222 million euros ($A355 million) deal from Barcelona and Kylian Mbappe from AS Monaco.
In June last year, the Investigatory Chamber of UEFA's Club Financial Control Body cleared PSG of breaking UEFA's break-even rules, yet later that month, the CFCB chairman ordered the Adjudicatory Chamber to review the decision.
The Adjudicatory Chamber then ruled in September that the case should be referred back to the Investigatory Chamber for further review.
PSG's appeal to have that decision annulled was upheld by CAS.
The club successfully argued that UEFA missed the deadline set out in the CFCB's Procedural Rules, which allow for a 10-day period during which any review should be instigated and completed.
UEFA said in a statement they would consider amending or clarifying their rules to avoid the same happening in the future.