Green, a 6-foot-4, 214-pound linebacker from Macon, Georgia, started seven games for the Wolfpack in 2011, totaling 28 tackles, one sack, and an interception.
He missed the final five games with an injury.
Green released a statement today on his situation.
"During the offseason, I wanted to gain weight so I took a supplement that someone from home gave to me," said Green. "I wasn't responsible enough to check with our coaches to make sure that it was something legal and now I'm paying the consequences.
"I apologize to my teammates, my coaches and to all the Wolfpack fans and hope that other players out there learn from my mistake. Even though it breaks my heart that I won't be able to play next year, I will work hard every day in practice to help try to make my teammates better."