While most of the instances of obstruction of justice occur in the form of perjury, most recently re "Scooter" Libby, prosecutors and attorneys general commited obstruction of justice when they failed to prosecute judges and other government officials for the "feasance trio" mentioned above.
The US Code Title 18, Chapter 73, Paragraph 1505 states that "whoever corruptly, or by threats or force, or by any threatening letter or communication influences, obstructs, or impedes the due and proper administration of the law under which any pending proceeding is being had before any department or agency of the United States, or the due and proper exercise of the power of inquiry under which any inquiry or investigation is being had by either the House, or any committee of either House or any joint committee of the Congress shall be fined under this title, imprisoned not more than 5 years or, if the offense involves international or domestic terrorism imprisoned not more than 8 years, or both."
In the case of either of these definitions the question arises, "Why isn't Nancy Pelosi obstructing justice when she continues to refuse to hold the hearings on impeachment for Bush and Cheney which have been presented to the House?"
That leads us to another huge case of obstructing justice in the case of Michael Muskasey, Attorney General, who refuses to hold hearings on a number of cases, namely the recent attorney hiring fiasco.
These are but two examples, as it is openly known that Bush and Cheney have spent their entire time in office withholding documents, preventing individuals from testifying, refusing to testify themselves before the 911 Commission (they did talk to at least a couple of them, but not under oath, and not with any notes taken or information removed from the close confines of their chat). I guess the main thing there was that Bush was "glad I took the time" to have the chat.
This is but another example of how far our democracy has crumbled under this regime. We have, evidently, closed the doors to any openness in our government.
