That’s another common misperception about Barry. He never was a professor, just a lecturer.
http://volokh.com/posts/1204053060.shtml
"Is that really true? He certainly wasn't an actual professor; you can't make it as a full-time Chicago law prof for 10 years with no legal publications. So at most he was an adjunct. Now did Chicago really have a need for an adjunct to teach Con Law? It's not as if they're hurting for great Con Law professors there."
He was a senior lecturer, a position usually reserved for a small number of instructors (such as Judges Easterbrook, Posner and Wood) who, because of other professional obligations, cannot commit to an ordinary professorship. He was reportedly offered tenure on several occasions, and declined.