(2) Government employee is an officer or employee of the United States or any agency of the United States, including a special government employee as defined in 18 U.S.C. 202(a), or of the District of Columbia, or of any State, or a member of Congress or of any State legislature.

(3) Member of a firm is a sole practioner or an employee or associate thereof, or a partner, stockholder, associate, affiliate or employee of a partnership, joint venture, corporation, professional association or other affiliation of two or more practitioners who represent non-Government parties.

(4) Practitioner includes any individual described in § 10.3(e).

(5) Official responsibility means the direct administrative or operating authority, whether intermediate or final, and either exercisable alone or with others, and either personally or through subordinates, to approve, disapprove, or otherwise direct Government action, with or without knowledge of the action.

(6) Participate or participation means substantial involvement as a Government employee by making decisions, or preparing or reviewing documents with or without the right to exercise a judgment of approval or disapproval, or participating in conferences or investigations, or rendering advice of a substantial nature.

(7) Rule includes Treasury Regulations, whether issued or under preparation for issuance as Notices of Proposed Rule Making or as Treasury Decisions, and revenue rulings and revenue procedures published in the Internal Revenue bulletin. Rule shall not include a transaction as defined in paragraph (a)(9) of this section.

(8) Transaction means any decision, determination, finding, letter ruling, technical advice, contract or approval or disapproval thereof, relating to a particular factual situation or situations involving a specific party or parties whose rights, privileges, or liabilities under laws or regulations administered by the Internal Revenue Service, or other legal rights, are determined or immediately affected therein and to which the United States is a party or in which it has a direct and substantial interest, whether or not the same taxable periods are involved. Transaction does not include rule as defined in paragraph (a)(7) of this section.

(1) No former Government employee shall, subsequent to his Government employment, represent anyone in any matter administered by the Internal Revenue Service if the representation would violate 18 U.S.C. 207 (a) or (b) of any other laws of the United States.

(2) No former Government employee who participated in a transaction shall, subsequent to his Government employment, represent or knowingly assist, in that transaction, any person who is or was a specific party to that transaction.

(3) No former Government employee who within a period of one year prior to the termination of his Government employment had official responsibility for a transaction shall, within one year after his Government employment is ended, represent or knowingly assist in that transaction any person who is or was a specific party to that transaction.

(4) No former Government employee shall, within one year after his Government employment is ended, appear before any employee of the Treasury Department in connection with the publication, withdrawal, amendment, modification, or interpretation of a rule in the development of which the former Government employee participated or for which, within a period of one year prior to the termination of his Government employment, he had official responsibility. However, this subparagraph does not preclude such former employee for appearing on his own behalf or from representing a taxpayer before the Internal Revenue Service in connection with a transaction involving the application or interpretation of such a rule with respect to that transaction: Provided, That such former employee shall not utilize or disclose any confidential information acquired by the former employee in the development of the rule, and shall not contend that the rule is invalid or illegal. In addition, this subparagraph does not preclude such former employee from otherwise advising or acting for any person.

(1) No member of a firm of which a former Government employee is a member may represent or knowingly assist a person who was or is a specific party in any transaction with respect to which the restrictions of paragraph (b)(1) (other than 18 U.S.C. 207 (b)) or (b)(2) of this section apply to the former Government employee, in that transaction, unless:

(2) No member of a firm of which a former Government employee is a member may represent or knowingly assist a person who was or is a specific party in any transaction with respect to which the restrictions of paragraph (b)(3) of this section apply to the former employee, in that transaction unless the firm isolates the former Government employee in such a way that he does not assist in the representation.

(3) When isolation of the former Government employee is required under paragraph (c)(1) or (c)(2) of this section, a statement affirming the fact of such isolation shall be executed under oath by the former Government employee and by a member of the firm acting on behalf of the firm, and shall be filed with the Director of Practice and in such other place and in the manner prescribed by regulation. This statement shall clearly identify the firm, the former Government employee, and the transaction or transactions requiring such isolation.