5 C.F.R. 2635.401
Conflict of Interest Provision
Employees cannot participate personally and substantially in a government matter the resolution of which would affect their own or imputed financial interests.
If your child owns IBM stock worth $16,000, you cannot be involved in computer acquisitions for the office. If you are on a leave of absence from a university, your re-employment rights are a financial interest. You must recuse from any grant or contract awards to your university. However, you may draft regulations affecting higher education in general, provided there is no special or distinct effect on your university. While seeking or negotiating for a non-government job, you cannot work on a matter at the Department that affects a prospective employer.
5 C.F.R. 2635.503
Prohibition on Salary Supplementation
Employees may not accept any contribution or supplementation of their government salary as compensation for services they perform officially.
While you may continue to participate in your former employer's bona fide pension and benefit plans, and receive appropriate severance payments paid by the company to all departing employees, you cannot receive a bonus paid to cushion the blow of a lower government salary.
18 U.S.C. 205
Representation, whether compensated or not, of private individuals or organizations in matters before the federal government is prohibited.
You cannot appear for a friend who is being audited by the IRS, inquire about your aunt's social security check, or represent a non-profit organization on a grant application before HHS or any other federal agency. However, you can help your friend fill out a tax form and assist your aunt in preparing an application for government benefits. You can always represent yourself, your parents, spouse, or children. If you are executor of a deceased uncle's estate, you are free to contact government agencies as a fiduciary.
18 U.S.C. 207
5 C.F.R. Part 2641
Former employees may not "switch sides" on matters they worked on or supervised. Former senior employees have additional “no contact” restrictions. Depending on prior pay status and the degree to which the post-employment activities touch upon former federal responsibilities, the restraints could last permanently, two years, or one year.
If you approved a grant application and thereafter go to work for the grantee, you can advise the grantee how to carry out the project properly and how to adhere to government procedures; you may not, however, sign any documents directed back to the agency requesting grant modifications or make calls asking for additional funding.