5 U.S.C. Appx § 502. Limitations on outside employment
(a) Limitations.—A Member or an officer or employee who is a noncareer officer or employee and who occupies a position classified above GS–15 of the General Schedule or, in the case of positions not under the General Schedule, for which the rate of basic pay is equal to or greater than 120 percent of the minimum rate of basic pay payable for GS–15 of the General Schedule shall not—
(1) receive compensation for affiliating with or being employed by a firm, partnership, association, corporation, or other entity which provides professional services involving a fiduciary relationship;
(2) permit that Member's, officer's, or employee's name to be used by any such firm, partnership, association, corporation, or other entity;
(3) receive compensation for practicing a profession which involves a fiduciary relationship;
(4) serve for compensation as an officer or member of the board of any association, corporation, or other entity; or
(5) receive compensation for teaching, without the prior notification and approval of the appropriate entity referred to in section 503.
(b) Teaching Compensation of Justices and Judges Retired From Regular Active Service.—For purposes of the limitation under section 501(a), any compensation for teaching approved under subsection (a)(5) of this section shall not be treated as outside earned income—
(1) when received by a justice of the United States retired from regular active service under section 371(b) of title 28, United States Code;
(2) when received by a judge of the United States retired from regular active service under section 371(b) of title 28, United States Code, for teaching performed during any calendar year for which such judge has met the requirements of subsection (f) of section 371 of title 28, United States Code, as certified in accordance with such subsection; or
(3) when received by a justice or judge of the United States retired from regular active service under section 372(a) of title 28, United States Code.
(Pub. L. 95–521, title V, §502, as added Pub. L. 101–194, title VI, §601(a), Nov. 30, 1989, 103 Stat. 1761; amended Pub. L. 101–280, §7(a)(1), (b), May 4, 1990, 104 Stat. 161; Pub. L. 101–650, title III, §319, Dec. 1, 1990, 104 Stat. 5117; Pub. L. 102–198, §6, Dec. 9, 1991, 105 Stat. 1624; Pub. L. 102–378, §4(b)(3), Oct. 2, 1992, 106 Stat. 1357.)