(1) Assist means to act in such a way as to advise, furnish information to, or otherwise aid another person, directly or indirectly.

(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 practitioner 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 nongovernmental parties.

(4) Practitioner includes any individual described in paragraph (f) of § 10.2.

(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; revenue rulings; and revenue procedures published in the Internal Revenue Bulletin. Rule does not include a transaction as defined in paragraph (a)(8) of this section.

(8) Transaction means any decision, determination, finding, letter ruling, technical advice, Chief Counsel advice, or contract or the 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.

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

(3) A former Government employee who within a period of one year prior to the termination of Government employment had official responsibility for a transaction may not, within two years after his or her 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 may, within one year after his or her 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 or her Government employment, he or she had official responsibility. This paragraph (b)(4) does not, however, preclude such former employee from appearing on his or her 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 does not utilize or disclose any confidential information acquired by the former employee in the development of the rule.

(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)(2) or (3) of this section apply to the former Government employee, in that transaction, unless the firm isolates the former Government employee in such a way to ensure that the former Government employee cannot assist in the representation.

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