(a) Subject to section 500 of title 5, the Secretary of the Treasury may - (1) regulate the practice of representatives of persons before the Department of the Treasury; and (2) before admitting a representative to practice, require that the representative demonstrate - (A) good character; (B) good reputation; (C) necessary qualifications to enable the representative to provide to persons valuable service; and (D) competency to advise and assist persons in presenting their cases. (b) After notice and opportunity for a proceeding, the Secretary may suspend or disbar from practice before the Department a representative who - (1) is incompetent; (2) is disreputable; (3) violates regulations prescribed under this section; or (4) with intent to defraud, willfully and knowingly misleads or threatens the person being represented or a prospective person to be represented. (c) After notice and opportunity for a hearing to any appraiser with respect to whom a penalty has been assessed under section 6701(a) of the Internal Revenue Code of 1986, the Secretary may - (1) provide that appraisals by such appraiser shall not have any probative effect in any administrative proceeding before the Department of the Treasury or the Internal Revenue Service, and (2) bar such appraiser from presenting evidence or testimony in any such proceeding.