TMZ has learned Justin Bieber's manager turned himself in to police this morning -- and it's all over unlawful Tweets ... allegedly.

Scott "Scooter" Braun surrendered on two misdemeanor charges -- reckless endangerment and criminal nuisance -- stemming from an incident at a mall in November.

The incident which triggered the matter occurred last November at the Roosevelt Field mall when fans got out of control and at least one girl was hospitalized.

We're told cops asked Braun to Tweet that the event had been canceled but they say he refused to do so.

Braun faces one year in jail if convicted.

UPDATE: The Bieb himself is finally weighing in -- Justin just posted the following Tweet: "You've got my total support @scooterbraun Wish you were here in Chicago with us #FreeScooter"