Mostert: Lyon has no claim
Golden Lions Rugby Union Chief Executive Rudolph Straeuli told rugby365 that they have a two-year contract with Mostert and he will return to the franchise for Super Rugby in February.
Mostert is currently "on loan" to the Black Rams in Japan.
Straeuli was reacting a report that the French club, Lyon, had threatened with legal action, because Mostert had not reported for duty at the team's Matmut Stadium in the Rhône-Alpes.
Lyon Olympique Universitaire, or LOU as they are often referred two, spat the dummy this week when they noted that Mostert is in Japan.
"Lyon Rugby notes with alarm that Franco Mostert is in Japan and is training with the Black Rams, while he has committed to two years with our club," the club said on their website.
"Faced with this serious violation of contract, law and basic values of rugby which are that a commitment is respected, the club will take all the necessary measures to see justice is done and is approaching the competent legal and rugby authorities," the terse statement concluded.
Contacted by the French news agency AFP, Lyon refused to give details on which authorities they had approached.
Straeuli hit back, claiming that Lyon is in fact on the wrong side of the law.
The 25-year-old lock, who has four Springbok caps since his debut against Ireland in June, was 'unveiled' by the French club as a new signing in March.
"Franco [Mostert] has signed with us [GLRU] for the next two years and is currently on loan in Japan," Straeuli told rugby365.
"He was under contract with us when they [Lyon] made the announcement that he has signed with them," the Lions boss said, adding: "According to World Rugby's regulations you can't sign a contract with a player while he is still under contract with another team.
"If you want to negotiate with a player under contract, you need to give notice to that team and they never gave us notice – which means they were in breach of the regulations.
"They did not follow the correct procedures."
Straeuli confirmed that there have since been communications between the French club and the GLRU.
"We pointed out the Lions' legal position on the matter," Straeuli said, adding: "They are aware of the fact that we feel they are at fault."
By Jan de Koning