Hatem Ben-Arfa's lawyer has accused Paris Saint-Germain of violating France's professional football charter in its treatment of the 30-year-old outcast.
The former Les Bleus star rejected the chance to leave during the transfer window and was subsequently demoted to PSG's reserve side, which competes in the fourth-tier Championnat National 2.
Jean-Jacques Bertrand, Ben Arfa's lawyer, labelled the move a contravention of Ligue de Football Professionnel (LFP) rules which prevent clubs from denying professionally-contracted players access to certain training standards.
Bertrand intends to appeal to the LFP's legal commission if the former Newcastle United and Nice playmaker is not restored to first-team training by Friday.
"Legally, I think the club is violating the Professional Football Charter," Bertrand told AFP.
"I informed the club by e-mail and advised that we do not accept the situation.
"Depending on the response, we will seek action from the league's disciplinary committee."
Speaking on the day of Kylian Mbappe's unveiling, PSG boss Unai Emery responded by saying the club had informed Ben Arfa of the situation at the beginning of pre-season and that he may still be recalled to first-team training.
However, Bertrand labelled the comments "comical".
"Half of the team are with their national teams and [other] players have been called up from the reserves to complete the group. Obviously it is not a problem of overstaffing," Ben Arfa's representative said.
The 15-time France international has less than 12 months remaining on his contract and was left out of PSG's squad for the Champions League group stage.