Matthew Charles turned his life around after serving 21 years in prison. Now, he’s headed back behind bars because of a technicality.

Charles, who served twenty years for selling crack to an informant, has made the best of the past two years, according to Nashville Public Radio.

Following his release in 2016, Charles got a job, volunteered every Saturday, bonded with his family, began a relationship and found God. Prior to his release, he never had any behavioral infractions during his time as an inmate. He took college classes, taught a GED program to fellow inmates and became a law clerk who assisted other inmates with their legal troubles.

Still, his efforts weren’t enough to keep him from returning to prison.

Charles’ initial release was the result of crack guideline changes that were passed under the Obama administration.

However, Charles had been to prison before the 21 years he served for selling crack. Because of this prior stint, the U.S. Attorney’s office appealed his 2016 release. The government argued the Obama-era change did not apply to Charles because he was a “career offender.”

In March, the U.S. Court of Appeals agreed with this argument, and ruled Charles must serve out the remainder of the 35 years he was sentenced to in the crack case. He has been given 45 days to get his affairs in order.

The judge who handed down the decision called the situation “sad,” and said Charles had an “exemplary rehabilitation.” However, she imposed his original sentence because “her hands were tied.”

“It was like a 180 from what I had thought would happen. I’m just disappointed, again,” he said outside the courtroom, at the time.

"But I believe that God is still in charge of the situation. He hasn't revealed to me what he's doing yet, but my faith remains the same."

Charles has turned himself in, and will serve the remainder of his sentence in a medium security prison in Kentucky, nine hours away from his Nashville home.

Calls have been growing asking for Charles' sentence to be commuted, and a Change.org petition hopes to pressure President Trump into pardoning him. Unfortunately, the White House has yet to comment on Charles' case.