The best way to answer the question you have asked is to carefully read the bylaws of your presumed corporation as to duties owed by members of the board to the corporation. From what you have written, it seems as though the board member breached a fiduciary duty to the corporation and its shareholders warranting the board member to lose his or her position as a director/board member.As to unilaterally taking back the board member's equity in the corporation, that cannot be done. A lawsuit first needs to be filed against the board member if warranted and if there is a judgment against him or her, the equity that the board member holds can be levied upon. I suggest that you consult with a business attorney about your situation involving the disgruntled board member.