20 Op. O.L.C. 379: Service on the Board of Directors of Non-Federal Entities by Federal Bureau of Investigation Personnel in their Official Capacities

Section 208 of title 18 prohibits a government employee from serving on the board of directors of an outside organization in his or her official capacity, unless the service is authorized by statute or the employee obtains either a release of fiduciary obligations by the organization or a waiver of the requirements of section 208.

https://www.justice.gov/file/19911/download