Following some lengthy, in-depth investigative work, USA Today has discovered more than 60 North Carolina men serving federal sentences for violating gun laws it turns out they didn’t actually violate:

The legal issues underlying their situation are complicated, and are unique to North Carolina. But the bottom line is that each of them went to prison for breaking a law that makes it a federal crime for convicted felons to possess a gun. The problem is that none of them had criminal records serious enough to make them felons under federal law.

Still, the Justice Department has not attempted to identify the men, has made no effort to notify them, and, in a few cases in which the men have come forward on their own, has argued in court that they should not be released.

Justice Department officials said it is not their job to notify prisoners that they might be incarcerated for something that they now concede is not a crime. And although they have agreed in court filings that the men are innocent, they said they must still comply with federal laws that put strict limits on when and how people can challenge their convictions in court.

"We can't be outcome driven," said Anne Tompkins, the U.S. attorney in Charlotte. "We've got to make sure we follow the law, and people should want us to do that." She said her office is "looking diligently for ways, within the confines of the law, to recommend relief for defendants who are legally innocent."

Hat tip to Radley Balko, who tweeted that horrifying, eye-catching quote from Tompkins. Of course, prosecutors are never “outcome driven” when they’re trying to throw defendants into prison, are they?

North Carolina’s unusual sentencing system is partly the cause of the problem. In order to try to standardize a federal law forbidding gun ownership by felons, the U.S. government needed to craft legislation that accounted for different states’ definitions of felonies. They settled on a law that made it illegal for a person to own a gun if they commit a crime that could have landed them a year or more of prison time:

Figuring out who fits that definition in North Carolina is not as simple as it sounds. In 1993, state lawmakers adopted a unique system called "structured sentencing" that changes the maximum prison term for a crime, based on the record of the person who committed it. People with relatively short criminal records who commit crimes such as distributing cocaine and writing bad checks face no more than a few months in jail; people with more extensive records face much longer sentences.

For years, federal courts in North Carolina said that did not matter. The courts said, in effect: If someone with a long record could have gone to prison for more than a year for the crime, then everyone who committed that crime is a felon, and all of them are legally barred from possessing a gun.

Last year, the U.S. Court of Appeals for the 4th Circuit said federal courts (including itself) had been getting the law wrong. Only people who could have actually faced more than a year in prison for their crimes qualify as felons under federal law.

Read through the story for the case of Terrell McCullum, a minor criminal who ended up in federal prison for possessing a firearm. Even his own lawyers thought he had broken the law due to a previous conviction for gun theft. (He’s not exactly the most sympathetic case. After a supervised release, he ended up back in jail for robbery and can probably no longer be considered a minor criminal.)

Whether McCullum — or the dozens of others like him — can go home depends on federal laws that put strict limits on when and how people who have already been convicted of a crime can come back to court to plead their innocence.

Those laws let prisoners challenge their convictions if they uncover new evidence, or if the U.S. Supreme Court limits the sweep of a criminal law. But none of the exceptions is a clear fit, meaning that, innocent or not, they may not be able to get into court at all. Federal courts have so far split on whether they can even hear the prisoners' cases.

So apparently misapplying the law in the first place doesn’t count as “new evidence.”