The Italian striker can be seen pointing the gun at the camera in the photo, which was accompanied with the message ‘big kiss to all the haters’.
The 23-year-old later deleted the post. The move has angered Balotelli’s employers AC Milan but vice president Adriano Galliani admits the club are powerless to stop players using social networks.
Galliani said: “I have my own ideas about social networks and I’ve tried many times but our lawyer has always stopped me, saying that it would violate individual rights.
“In contracts it’s written what players can and cannot do, but we can’t do anything regarding their private lives. We do it vocally but that’s not enough.”
The incident is the latest in a long history of controversies involving Balotelli, who in 2011 during his time at Manchester City was caught throwing darts at a youth team player.
Balotelli is currently on holiday in Miami with fiancé Fanny Neguesha after Italy crashed out of the World Cup in the group stages. Balotelli scored the winner in a 2-1 win for Italy against England on June 15.