Sam Sloan wrote:

When is it appropriate to ban a player from a chess club?

The statues of the club should make it clear. Typically,
a member who is consistently acting against the interest
of the club, or whose influence in other ways on the
club, society or organization will be detrimental
can be expelled.

Banning -- i.e. temporary suspension of membership privileges --
seems like an appropriate measure against first offences of
a nature that, once it's clear it is deliberate and wilful,
would cause explusion.

--
Anders Thulin http://www.algonet.se/~ath