Justin Bieber Plays Underage Drinking Game

Even though he's underage, we know Bieber pounded some beer during the game ... just like every other underage college kid across the country.

The question -- which country? One source connected with Bieber -- who was not there -- says the game went down on Canadian soil ... or in Georgia (he travels a lot, it's hard to keep track). Either way, the source says it happened a year and a half ago, which would have made Bieber 17-years-old ... and too young to legally booze in either country.