As Pike’s committee report stated: “These secret agencies have interests that inherently conflict with the open accountability of a political body, and there are many tools and tactics to block and deceive conventional Congressional checks. Added to this are the unique attributes of intelligence — notably, ‘national security,’ in its cloak of secrecy and mystery — to intimidate Congress and erode fragile support for sensitive inquiries.
“Wise and effective legislation cannot proceed in the absence of information respecting conditions to be affected or changed. Nevertheless, under present circumstances, inquiry into intelligence activities faces serious and fundamental shortcomings.
“Even limited success in exercising future oversight requires a rethinking of the powers, procedures, and duties of the overseers. This Committee’s path and policies, its plus and minuses, may at least indicate where to begin.”
The Pike report revealed the tactics that the intelligence agencies had used to prevent oversight, noting the language was “always the language of cooperation” but the result was too often “non-production.” In other words, the agencies assured Congress of cooperation, while stalling, moving slowly, and literally letting the clock run out on the investigation.
The Pike Committee, alone among the other investigations, refused to sign secrecy agreements with the CIA, charging that as the representatives of the people they had authority over the CIA, not the other way around.
The Senate's Church Committee gets all the publicity but the House Pike Committee did much of the heavy lifting in the mid-1970s investigation of spy agency abuse. This is a good solid overview of that committee's work in historical context and a troubling reminder that the NSA's current confrontational tactics with Congress are nothing new.