I completely agree with Tim.  In fact we were taught in our museum science
classes that you can fire a volunteer as they are legally speaking anyway (in
terms of liability) "unpaid staff".  I think that when a new volunteer comes
your way, it would be beneficial for them to have to fill out some very basic
paperwork (including object handling rules or rules of the museum, etc.) that
states in the result of unsatisfactory behavior (etc.) they can and will be
terminated.  Then the issue has been raised and everyone is aware of what can
happen.

Ginger M. Young, Registrar