18 U.S.C. § 602

(a) It shall be unlawful for— (1) a candidate for the Congress; (2) an individual elected to or serving in the office of Senator or Representative in, or Delegate or Resident Commissioner to, the Congress; (3) an officer or employee of the United States or any department or agency thereof; or (4) a person receiving any salary or compensation for services from money derived from the Treasury of the United States; to knowingly solicit any contribution within the meaning of section 301(8) of the Federal Election Campaign Act of 1971 from any other such officer, employee, or person. Any person who violates this section shall be fined under this title or imprisoned not more than 3 years, or both. (b) The prohibition in subsection (a) shall not apply to any activity of an employee (as defined in section 7322(1) of title 5 ) or any individual employed in or under the United States Postal Service or the Postal Regulatory Commission, unless that activity is prohibited by section 7323 or 7324 of such title.