1 Corinthians 5:11

But now I have written unto you not to keep company, if any man that is called a brother be a fornicator, or covetous, or an idolator, or a railer, or a drunkard, or an extortioner; with such an one no not to eat (KJV)

Then: Stoning is out; but the church had to do something. For its own good, it needed some kind of discipline. So, Paul killed two birds with one stone. Separate the sinner from the church body, and then it could get its reputation back. For the Corinthians not keeping company could have meant complete exclusion, no association of any kind. Thiselton (p. 408) translates the phrase as "mix indiscriminately"; that looks like absolutely no contact. "Eating" meant to observe the Last Supper. Every Sunday they got together in what may have been "potluck" meals to remember Christ by following his direction, "Do this in remembrance of me." Anyone who continually dishonors his/her committment to the Lord could no longer take part. Neither could they be included in other church activities.

Now: We just don't throw people out of the church. As difficult as it is to cut off family, business or civic relationships, it would seem impossible to maintain a ban against individual church members keeping company or mixing indiscriminately with those who have been disciplined by the church. Interpreting Paul's command gets even more tricky when we read Galatians 6:1-2 which reveals Paul's hope that believers can restore such a one as this. I think attention has to be paid to the idea of the direction being given to the church body and not to individual members. Complete isolation would abandon an individual and preclude all possibility of return into fellowship.

Extra source: The First Epistle to the Corinthians: a commentary on the Greek text by Anthony C. Thiselton (Authentic Media, c2000) online at http://books.google.com/books?id=IHG_DNLpmroC&dq=1st+Corinthian+commentaries&printsec=frontcover&source=in&hl=en&ei=W9fQSpC1GILplAfHiumoCg&sa=X&oi=book_result&ct=result&resnum=11&ved=0CB8Q6AEwCg#v=onepage&q=&f=false