Former France international Diarra, now 39, has been embroiled in a series of legal battles since his contract with Lokomotiv Moscow was terminated by the club in 2014.
Following a dispute with manager Leonid Kuchuk, Lokomotiv claimed Diarra refused to show up for training or accept a lower salary and sacked him three years before his deal was up.
In 2016, a Fifa ruling – supported by the Court of Arbitration for Sport (Cas) – found Diarra liable for breach of contract, ordered him to pay 10m euros (£8.4m) to Lokomotiv and banned him from professional football for 15 months.
When Diarra agreed to a deal to join Charleroi, the club sought assurances that it would not be liable to pay any compensation to Lokomotiv.
Fifa then refused to give Charleroi the ITC, required by clubs around the world to sign a new signing, so the deal fell through.
Diarra’s lawyers challenged this particular rule – which makes the club seeking to sign the player jointly liable for compensation to the player’s former club, and at risk of sporting sanctions, in cases where the player’s previous contract was terminated without just cause.
They also objected to a law allowing the national association of a player’s former club to block the ITC where there was a dispute, which they said also prevented the move.
The court has decided that Fifa cannot use the ITC system to prevent players who violated the contract from moving and working where they want.
Parts of Fifa’s transfer rules will have to be amended to remain valid in the European Union.
