"Habitual drug abusers, like the mentally ill, are more likely to have difficulty exercising self-control, making it dangerous for them to possess deadly firearms," the court said in the decision.

Court documents are unclear on whether Yancey got his gun legally, and his attorney didn't return calls. But carrying a sidearm openly is legal; carrying one concealed in your pants pocket clearly is not.

The feds took the case presumably because Yancey has a history of sometimes violent offenses as a juvenile. And while when he was caught with the gun he wasn't a felon -- which imposes a lifetime ban on owning a firearm -- he is now. In addition to the federal felony the court upheld, he pleaded no contest to one count of burglary in state court in 2008.

So Yancey won't be able to take advantage of this differentiation the court offered between the combined group of felons and the mentally ill and drug users:

"Unlike those who have been convicted of a felony or committed to a mental institution and so face a lifetime ban, an unlawful drug user like Yancey could regain his right to possess a firearm simply by ending his drug abuse."