The only meaningful post-government restrictions are Revolving Door statutes governing employment activities of former federal and many state employees. These statutes seek to prevent conflicts of interest (often called Switching Sides) by restricting post-government representational activities (such as lobbying) for private employers to influence current officials in the same agencies and/or on the same matters which the former government employee worked.
While it is important to note that these laws usually carry criminal penalties, they only apply to direct dealings with the former agency on matters over which the former employee exercised some degree of control while in government service.
Use of Data or Information
Unless working inside the intelligence community, former government employees are free to write memoirs, speak to the media or share their knowledge with future employers.
Government documents are not subject to copyright but note, however, that some work by government contractors may be. With very few exceptions, such as classified information or sensitive encrypted technology, information from inside government agencies may be published. Government restrictions, such as new categories like “controlled unclassified information”, have no further application to those who have left government service.
If there is any doubt about the public nature of information a former employee wishes to publish, he/she may simply file a Freedom of Information Act for the records or data in question.
Contrary to rumor (sometimes spread by agency HR people), a federal employee does not lose his/her pension rights if fired or involuntarily separated. The only basis for rescinding a pension right is conviction of a crime against the national security (treason, sedition, espionage, and other comparable crimes listed in 5 USC § 8312). In fact, federal employees convicted of wage fraud still receive their pension payments even while in prison.