John, Robert and Jackie Are the Only Shareholders of Camelot

John, Robert and Jackie are the only shareholders of Camelot Pty Ltd. John and Robert (who between them hold 80% of the issued shares in Camelot Pty Ltd) want to ensure the shares of Camelot Pty Ltd are not sold to Nixon Pty Ltd, a competitor of Camelot Pty Ltd. John and Robert can call a meeting of shareholders and pass a special resolution altering the constitution to provide that shareholders in Camelot Pty Ltd can transfer their shares to any person except Nixon Pty Ltd without the consent of the company and that amendment is enforceable.