A Columbian drug dealer is going back to the slammer. But no, it's not a Colombian dealer, it's the former Columbia University anthropology student, who was dealing pot from his International House dorm room, according to the New York Post.

He flunked his latest drug test.

Chris Coles got busted--caught selling pot by the pound out of the International House dorm--a felony.

He'd been allowed out while the courts decided on approving his treatment deal, that would have let him avoid jail. Now he's incarcerated until Dec. 22, his next court date.