Manchester United No.1 could be banned from playing for the English club because of a less-known Fifa law as the Cameroonian is pondering sitting out the tournament.
Andre Onana is expected to travel to the Africa Cup of Nations with Cameroon in January.
The former Ajax and Inter Milan man retired from international duty after quitting the team during the World Cup last year but has since returned to the squad after rebuilding his association with manager Rigobert Song.
Nonetheless, Onana could resolve to sit out of Afcon in a bid to concentrate on United, as his form has suffered since joining the club most notably his horrendous performance against Galatasaray which aided the Turkish side's comeback in the 3-3 draw in the UCL.
However, if Cameroon demands he play and Onana refuses, the goalkeeper could be forbidden from playing for the Red Devils by Fifa.
The official Fifa line reads: "A player who has been called up by his association for one of its representative teams is, unless otherwise agreed by the relevant association, not entitled to play for the club with which he is registered during the period for which he has been released or should have been released under the provisions of this annex, plus an additional period of five days.”
Onana is expected to miss six United games with Afcon running from January 13 to February 11 should he partake in the tournament.
The shot-stopper has floundered since his summer move and Premier League legend Ruud Gullit believes Erik ten Hag will have to start asking questions of his keeper.