Twenty-year-old midfielder Elmas could face a costly rap after being quoted by various outlets during his time away with Macedonia, despite telling reporters Napoli could still vie for the Serie A title.
The Naples club appears to be in disarray after first-team players rebelled en masse and quit a training retreat earlier this month.
That getaway to nearby Castel Volturno was ordered by club president Aurelio De Laurentiis, after a run of poor results, but it was dramatically cut short after a UEFA Champions League match against Salzburg.
Napoli hinted at taking legal action against its own squad, saying on 6 November it would "do everything in its power to protect its economic interests, assets, image rights and disciplinary interests", and ruling there would be no media communication "for the foreseeable future".
A goalless draw at home to Genoa followed for Carlo Ancelotti's team, leaving Napoli, which finished runner-up to Juventus last season, sitting seventh in Serie A.
In the latest twist, a statement attributed to head of communications Nicola Lombardo was posted by Napoli on Twitter, reading: "SSC Napoli can confirm that Eljif Elmas spoke to the press without the club's authorisation during the current media blackout.
"SSC Napoli therefore reserves the right to take action against the player."
Napoli's statement was issued barely half an hour before Elmas took to the pitch for Macedonia on Sunday (AEDT) in its UEFA Euro 2020 qualifier against Austria.
In his interview, widely reported in Italy, Elmas said Juventus was well placed to win another Serie A title but added: "There are so many teams in the fight: Inter, Napoli and Roma. The battle will be uncertain until the end."