Section 12. By any votes required under federal law and the filing of such documents as the commissioner shall prescribe and under such terms and conditions as the commissioner may impose, a federally-chartered bank or thrift institution, upon approval by the commissioner, shall be converted into a bank chartered pursuant to chapter 168, 170 or 172, and shall not, in connection with or upon such conversion, be subject to the requirements of the General Laws with respect to the organization and commencement of business of such a bank; provided, however, that such conversion shall comply with the laws of the United States.