It seems to me that the following would be reasons for excommunication in the scriptures as long as the person was flagrant and unrepentant in this regard:
1 Cor. 5:10 – A brother who is a:
Fornicator
Greedy
Idolater
Reviler
Drunkard
Extortioner
And 1 Tim. 5:20 –
Blasphemer
Then, in 2 John - anti-Christ
How do we know how far the 1st century Christians took excommunication back then? As far as the Anti-Christ goes, Christians would not receive them into there homes. However, in the case of the person who had relations with his fathers wife in Cor, was he allowed to say a greeting with the other members? Did "mix in company with" mean he wasn't allowed at the meetings, or that they weren't supposed to talk with him at all?
After how long was the excommunication ban lifted? Was he even repentant when the ban was lifted?
Also, it seems that the entire congregation made the judicial decisions. On what scriptural basis does JWs form a committee instead of the entire congregation?
If excommunication is used in the scriptires, would we not be getting the scriptures principles if we then didn't pass the same judgement on a murderer or rapist? And then, if judgement was passed on them, where would a line be drawn? Which sins would be fall under the excommunication rule?
And if sin is breaking a law according to the scriptures, which law shows the sins we are to stay away from - Noahs law or the Mosaic one?