From the Office of Government Ethics web site
An executive branch employee may not participate in any particular Government matter that will affect the financial interests of a person or entity with whom he is seeking employment. An employee is considered to be seeking employment if --
- the employee is engaged in actual negotiations for employment
- a potential employer has contacted the employee about possible employment and the employee makes a response other than rejection, and
- the employee has contacted a prospective employer about possible employment (unless the sole purpose of the contact is to request a job application or if the person contacted is affected by the performance of the employee's duties only as part of an industry).
An employee is considered no longer seeking employment if --
- either the employee or the prospective employer rejects the possibility of employment and all discussions of possible employment have ended, or
- two months have elapsed since the employee's dispatch of an unsolicited resume and the employee has received no expression of interest from the prospective employer.
In some cases, an employee may be authorized by an agency official to participate in particular matters from which he would otherwise have to be disqualified due to his job search. In other cases, an agency ethics official may determine that an employee who has sought, but is no longer seeking, employment nevertheless shall be subject to a continuing period of disqualification.
If a search firm or other intermediary is involved, the employee is not disqualified unless the intermediary identifies the prospective employer to the employee.
Reference: 18 U.S.C. § 208; 5 C.F.R. §§ 2635.601-606.
See also the OGE Pamphlet: Understanding the Revolving Door: How Ethics Rules Apply to Your Job Seeking and Post-Government Employment Activities (OGE web site, available in both pdf and text format)