Vacancies occurring on the Commission shall be filled in the same manner as the original appointment. A member may serve after the expiration of his term of office until his successor has been appointed, unless the member has been removed for cause under subsection (b)(6).
25 U.S. Code § 2704 - National Indian Gaming Commission
(b) Composition; investigation; term of office; removal
(1) The Commission shall be composed of three full-time members who shall be appointed as follows:
a Chairman, who shall be appointed by the President with the advice and consent of the Senate; and
two associate members who shall be appointed by the Secretary of the Interior.
Except as provided in subparagraph (B), the term of office of the members of the Commission shall be three years.
(5) No individual shall be eligible for any appointment to, or to continue service on, the Commission, who—
A Commissioner may only be removed from office before the expiration of the term of office of the member by the President (or, in the case of associate member, by the Secretary) for neglect of duty, or malfeasance in office, or for other good cause shown.
(e) Vice Chairman
All members of the Commission shall be reimbursed in accordance with title 5 for travel, subsistence, and other necessary expenses incurred by them in the performance of their duties.