(2) No former Government employee who personally and substantially participated in a particular matter involving specific parties may, subsequent to Government employment, represent or knowingly assist, in that particular matter, any person who is or was a specific party to that particular matter.
(3) A former Government employee who within a period of one year prior to the termination of Government employment had official responsibility for a particular matter involving specific parties may not, within two years after Government employment is ended, represent in that particular matter any person who is or was a specific party to that particular matter.
(4) No former Government employee may, within one year after Government employment is ended, communicate with or appear before, with the intent to influence, any employee of the Treasury Department in connection with the publication, withdrawal, amendment, modification, or interpretation of a rule the development of which the former Government employee participated in, or for which, within a period of one year prior to the termination of Government employment, the former government employee had official responsibility. This paragraph (b)(4) does not, however, preclude any former employee from appearing on one's own behalf or from representing a taxpayer before the Internal Revenue Service in connection with a particular matter involving specific parties involving the application or interpretation of a rule with respect to that particular matter, provided that the representation is otherwise consistent with the other provisions of this section and the former employee does not utilize or disclose any confidential information acquired by the former employee in the development of the rule.