Too secret to be investigated by anyone

I find this really interesting. The Justice Department has been forced to cancel an investigation into the NSA spying controversy because the NSA refuses to give the Justice Department lawyers the needed security clearances.

WASHINGTON - The government has abruptly ended an inquiry into the warrantless eavesdropping program because the National Security Agency refused to grant Justice Department lawyers the necessary security clearance to probe the matter.

That's certainly convenient, isn't it? The agency that can never be investigated because everything it does is self-proclaimed to be too secret to be known by anyone. That's the perfect cover, isn't it?

I suppose the same thing will apply if Congress ever gets the balls to conduct an investigation.