New Zealand great Dan Carter and two other players from French side Racing 92 are to take their case to the public prosecutor after confidential medical records were made public by media, their club announced.
Carter, fellow former All Black Joe Rokocoko and Argentinian winger Juan Imhoff were the target of an investigation by the medical commission of the French Rugby Federation after testing positive for corticosteroids following last season's domestic Top 14 final.
But the trio, as well as Racing's medical staff, were all cleared of any wrongdoing.
The club said in a statement that media reports had "blurred public perceptions of their players."
The statement added that they and the players had decided to take action "in order to shine light on how their medical confidentiality was breached."