I am not an attorney, and don't play one on the internet, and this is not legal advice....   That being said, one aspect that people often overlook in "Code of Conduct" discussions is the legal liabilities involved.  Let's say person A organizes a conference and decides (for whatever reason) that person B needs to be banned.  Person B comes back later (or next year, or three years down the road) -- who is responsible to check to make sure person B hasn't been blacklisted?  Who is responsible to check to make sure person B isn't registering under a different name?  If person B were to do something illegal upon returning, person A might have additional legal liabilities. 

I mention all this not to discourage the use of codes of conduct -- but to help people remember that trying to ban someone might incur additional responsibilities (and liabilities), which might be hard on a loosely-formed mostly-volunteer group.  It's unfortunate that we live in such a litigious society... and that it's harder to do the right thing because of it.

-Jared