(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) Particular matter involving specific parties is defined at 5 CFR 2637.201(c), or superseding post-employment regulations issued by the U.S. Office of Government Ethics.

(5) Rule includes Treasury regulations, whether issued or under preparation for issuance as notices of proposed rulemaking or as Treasury decisions, revenue rulings, and revenue procedures published in the Internal Revenue Bulletin (see 26 CFR 601.601(d)(2)(ii)(b)).

(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.

(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 particular matter(s) requiring isolation. The statement must be retained by the firm and, upon request, provided to the office(s) of the Internal Revenue Service administering or enforcing this part.