CAS has ruled in favour of Paris Saint-Germain after they challenged UEFA's decision to reopen a previous Financial Fair Play probe.
Paris Saint-Germain's appeal against UEFA's decision to reopen an investigation into alleged breaches of Financial Fair Play rules has been upheld by the Court of Arbitration for Sport (CAS).
UEFA confirmed last September that it was looking again at a probe into PSG's financial conduct, which was first opened in September 2017 in the wake of the world-record €222million signing of Neymar and the €180m loan-to-buy deal for Kylian Mbappé.
UEFA's Club Financial Control Board closed the investigation last June after deciding PSG had complied with FFP rules but reopened it after a review.
However, CAS has now ruled that the original decision to close the case is "final and binding" after upholding PSG's claim that the CFCB's request for a review was made outside of a stipulated 10-day time limit.
In a statement released on Tuesday, CAS said: "The appeal filed at CAS on October 3 2018 by Paris Saint-Germain against the decision issued on September 19 2018 by the Adjudicatory Chamber of the UEFA Club Financial Control Body (CFCB) (the Challenged Decision) is upheld and the Challenged decision is set aside.
"The decision issued on 13 June 2018 by the Investigatory Chamber of the UEFA CFCB in which the investigation into Paris Saint-Germain's compliance with the UEFA Financial Fair Play regulations was closed is thus final and binding.
"On June 22 2018, the Chairman of the UEFA CFCB, on the basis of Article 16 (1) of the UEFA CFCB Procedural Rules (the Applicable Rules), ordered that the Adjudicatory Chamber review the decision taken by the Investigatory Chamber on 13 June 2018. The Adjudicatory Chamber ruled on September 19 2018 that the case should be referred back to the Investigatory Chamber for further investigation.
"On October 3 2018, Paris Saint-Germain filed an appeal at the CAS seeking to have such decision annulled on the basis that Article 16 (1) provided for a 10-day review period during which any review should be instigated and completed and that the Challenged Decision was manifestly late.
"The CAS Panel in charge of the matter issued its decision on the basis of the parties' written submissions. The CAS Panel concurred that the 10-day time limit which starts to run from the date of communication of the decision of the Chief Investigator to the CFCB Chairman, as set out in Article 16 (1) of the Applicable Rules, did indeed mean that the review conducted by the Adjudicatory Chamber should have taken place within ten days and that since the Challenged Decision was issued beyond the 10-day time limit, the Challenged Decision was untimely and must be annulled."
UEFA's initial investigation was to examine whether PSG had flouted rules aimed at preventing clubs from spending more than they generate through revenues.
The regulations were introduced to prevent clubs becoming at risk of financial instability through unmanageable spending, although they have been criticised by some who claim they inhibit teams from competing with the established European elite.
In 2014, PSG were fined €60m and saw their Champions League squad size reduced after a previous separate UEFA investigation into alleged FFP breaches.
The Parc des Princes club has invested significantly in the playing squad since being taken over by Qatar Sports Investments in 2011.