Julian Sanchez at Cato with some bitter but worthwhile examples of how checks and balances really work when it comes to congressional oversight on executive action, especially when "national security" is (supposedly) involved:

Blogger Mike Masnick recently came across a series of talking points that the National Security Agency provided its putative “overseers” on the congressional intelligence committees back when it first became known that President George W. Bush had authorized an unlawful warrantless surveillance program.  (These talking points have apparently been publicly available for some time, but have escaped attention.)

Some pieces of NSA’s script for its legislative vassals are merely humorous. For instance:

I have personally met the dedicated men and women of the NSA. The country owes them an enormous debt of gratitude for their superb efforts to keep us all secure.

One perk of this sort of ventriloquism, I suppose, is that you can dispense entirely with modesty when heaping praise on yourself.

Other points on the list, however, appear to be outright falsehoods.  For instance:

I can say that the Program must continue. It has detected terrorist plots that could have resulted in death or injury to Americans both at home and abroad.

As best we can tell from the unclassified version of the Inspectors General’s Report on the President’s Surveillance Program, this is not true.  Rather, while it appears to have had somevalue, the program “generally played a limited role in the FBI’s overall counterterrorism effort,” and “was rarely the sole basis for an intelligence success.” On the whole, it “was not of greater value than other sources of intelligence,” and “most [intelligence] officials had difficulty citing specific instances where [the program] had directly contributed to counterterrorism successes.” .....

Returning to the talking points, there’s this:

The Program is not “data mining”; it targets only international communications closely connected to al Qai’da or an affiliated group.

Two deceptions for the price of one! As we now know, the original “Stellar Wind” program did indeed involve data mining as well as warrantless wiretapping. Once the program was revealed, however, intelligence officials retroactively decided to make up something called the “Terrorist Surveillance Program” as a label for only the warrantless wiretapping component of the program. Then, even though the NSA surveillance program did involve data mining, they could claim that the “Terrorist Surveillance Program” didn’t use data mining, because they’d defined it (without telling anyone) as the non-data-mining parts of the real larger program....

Also, as the Inspectors General concluded, “most [of the surveillance program's] leads were determined not to have any connection to terrorism.” 

Reason on the NSA.

I wrote for Reason all the way back in 1992 on Congress' general tendency to become ideological prisoners of what they tend to hear from lobbyists of all sorts; and the most dangerous lobby in Washington is, as always, the government itself.