Justin Bieber -- Separated From Bodyguard ... BLOCKED By Canada

Justin Bieber has been separated from the bodyguard who has become his biggest confidante ... because Canada thinks the guy is just too violent.

Hugo Hesney faces felony charges for 2 separate assaults ... one against a photog and another against a cop.

Hesney tried to accompany Bieber when he flew to Toronto earlier in the week, but we're told authorities turned him away at customs because of the pending criminal cases. So Bieber bought him a one way commercial ticket back to the U.S.

Hesney has become Bieber's main man ... not just a bodyguard but someone Bieber relies on for advice. Bieber said in his now-infamous deposition ... he trust Hesney to give him straight answers.