Springboks star Johan Goosen was threatened with legal action by Racing 92 on Friday after his shock decision to quit the sport and return to South Africa.
The 24-year-old was reported to be taking up a commercial director's job in South Africa, a decision which left French champions Racing fuming.
"Johan Goosen, whose contract was renegotiated less than a year ago, now claims to be releasing himself in an extraordinary manner by announcing he has made the unbelievable decision to return to South Africa for a role of commercial director," said Racing president Jacky Lorenzetti.
"Racing 92 reserves the right for a judicial follow-up to both Johan Goosen and those who advise him.
"Racing have always supported Johan Goosen both morally and financially, even though he has unfortunately demonstrated lately a certain lack of responsibility.
"Hopefully he will quickly realise that respect for a contract, like that of the given word, is the basis of all relationships."
Fly-half star Goosen was Top 14 player of the year last season as Racing won the French title and reached the European Champions Cup final.
He joined Racing in 2014 from the Cheetahs and has won 13 caps for the Springboks.
However, Goosen was believed to be disenchanted by a lack of playing time following the arrival of All Blacks star Dan Carter.
Racing's kicking coach Ronan O'Gara said he was stunned by the controversy.
"I only found about it on Twitter and I am part of the Racing management team," the Irishman told BT Sport ahead of Friday's European Champions Cup clash against Glasgow.
"There has been a lot of unrest, but this has shocked us. When he is in the right frame of mind, we need him."