The process and cause for expelling a member are usually set out in the state nonprofit corporation law or the bylaws of the organization or a combination of both.  Ordinarily, a court will not interfere with the action of an organization in expelling a member if the organization follows its required procedures and provides some modicum of due process.  (See article this issue, February 16-28, 2010.)  If the organization acts arbitrarily, however, a court is much more likely to overturn the action.