; vacancies After its initial meeting, the Commission shall meet upon the call of the Chair or a majority of its members. Eighteen members of the Commission shall constitute a quorum, and members shall have the option to vote by proxy. Any vacancy in the Commission shall not affect its powers, but shall be filled in the same manner in which the original appointment was made. (g) Powers of Commission (1) In general (A) Hearings and evidence The Commission or, on the authority of the Commission, may, for the purpose of carrying out this section— (i) hold such hearings and sit and act at such times and places, take such testimony, receive such evidence, administer such oaths; and (ii) subject to subparagraph (B), require, by subpoena or otherwise, the attendance and testimony of such witnesses and the production of such books, records, correspondence, memoranda, papers, and documents. (B) Subpoenas (i) Issuance (I) In general A subpoena may be issued under this subsection only— (aa) by the agreement of the Chair and the Vice Chair