No, selling used mp3s has not been found legal. If you trace the link's back to the original source you get this article at Ars:

**Judge denies record label's request to shutter "used" MP3 store**

http://arstechnica.com/tech-policy/news/2012/02/judge-denies-record-labels-request-to-shutter-used-mp3-store.ars

The judge still thinks ReDigi's arguments are likely to fail and that Capitol Records will prevail. The only thing that is significant is that ReDigi's case isn't over yet at the motion stage.

I'm not sure if people get how crazy dangerous even a low end class 4 laser is to people's eyesight. Even diffuse reflections can cause blindness. And blindness from a direct beam or specular reflection is virtually instant, literally before you can blink. This laser is not a toy. Not something you can casually show off safely to your friends. You can blind people, forever, accidentally, in an instant. Just keep it in mind.

"From TFA: Years ago, college students were our best customers," he said. "Now they're among our worst customers.""
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Well, of course the RIAA is selling fewer units per capita. The number of media choices competing for the a person's money is far greater than it has ever been. The RIAA is blaming its dwindling share of wallet on piracy instead of the fractionalization of the market. They can sue 20,000 people and that won't change--the proof being they did and it hasn't.