Prosecutors and defense lawyers agree that a federal judge in Washington made a mistake when he sentenced Derrek Arrington to two back-to-back terms of supervised release. (They could only run concurrently.) But the U.S. Court of Appeals for the D.C. Circuit on Friday said it was powerless to fix the error.

Arrington was convicted in 2000 of assaulting a federal officer and unlawfully possessing a firearm as a convicted felon. Now-retired U.S. District Judge James Robertson sentenced him to 20 years in prison followed by two consecutive three-year terms of supervised release.

The problem was that, under federal law, the judge could only sentence Arrington to concurrent terms of supervised release. The judge also erred in explaining his decision to sentence Arrington to 20 years in jail–he initially said that was the maximum sentence for one of the offenses Arrington was convicted of, but that wasn’t true. The judge later corrected himself and defended the sentence as proper because it was the sum of two consecutive 10-year sentences.

Arrington’s case eventually reached the D.C. Circuit. In Friday’s decision, Judge Sri Srinivasan, writing for the three-judge panel, acknowledged that both sides agreed the consecutive terms of supervised release weren’t allowed. But Srinivasan wrote that the court couldn’t provide any relief under the federal rules he cited.

Rule 36 of the Federal Rules of Criminal Procedure, for example, allows the court to correct a “clerical error.” The problem, Srinivasan said, was that Robertson’s mistake wasn’t a clerical error. “To the contrary, the court plainly intended to sentence Arrington to consecutive three-year terms of supervised release, and the written order accurately reflects the court’s intention,” he wrote.

Arrington’s only recourse, according to the court, was to go back to the judge currently assigned to the case (Senior Judge Royce Lamberth took over for Robertson in 2010) to ask him to change the length of his supervised release, which he could only do after serving his first year of supervised release.

According to the Federal Bureau of Prisons, Arrington is scheduled to be released from custody in 2017.

The D.C. Circuit panel rejected Arrington’s other challenges. Chief Judge Merrick Garland and Judge Patricia Millett also heard the case.

Arrington’s case was argued in March by Ben Thorpe, who at the time was a student at the University of Georgia School of Law. He recently began clerking for Judge Frank Hull of the Eleventh Circuit. The law professor who oversaw his work through the school’s Appellate Litigation Clinic, Erica Hashimoto, declined to comment on the ruling.

A spokesman for the U.S. attorney’s office in Washington said they were reviewing the opinion and had no other comment.

Contact Zoe Tillman at