From Sibel re Russ Tice (link):
First Time Released Documents Expose Subservient Congress
"National Security" Converts the United States into a Monarchy
National Security Whistleblowers Coalition (NSWBC) has obtained documents revealing that to date the Executive Branch has refused congressional requests to be briefed on illegal black operations conducted by the NSA, and has denied these representatives access to relevant witnesses and documents. To view these documents click here (pdf).
The term "national security" has become talismanic, conferring extraordinary powers on the President whenever it is uttered. It insulates the executive branch from congressional oversight and reduces the Constitution to advisory status. The circularity of the term’s operation is frequently overlooked. Information and programs are classified according to presidential orders and when Congress or the judiciary seeks such information they are told that because the information is classified, national security forbids disclosure. Even the Code of Federal Regulations identifies national security information as information that is classified pursuant to executive orders. In other words, the material is classified and unavailable because the President says so; no reasons need to be supplied. This prevents Congress from having access to the material, for even the two select committees for oversight of intelligence activities are shunned when they request documents.
In this link you see various letters from members of Congress and the executive branch, with bureaucrats refusing information to the two intelligence oversight committees because the committee members do not have appropriate clearances. Of course, clearances, like classified information, are exclusively controlled by the President. So if he does not want oversight of anything he has made secret he simply refuses Congress clearance to see the material. This is the modern version of Royal Prerogative that was argued by Parliament against Charles I in 17th century England and was finally, so we thought, put to rest in the United States by the Constitution. "National security" has converted the presidency into a limited monarchy with the power to deny the people, through their elected representatives, accountability for executive actions.
These letters show that oversight of Special Access Programs (SAPs) at the Department of Defense is nonexistent because no one in congress has a high enough security clearance. It highlights the nightmare that Russ Tice, former National Security Agency (NSA) intelligence analyst and a member of NSWBC, went through to find someone in congress to whom he could address illegal and unconstitutional activity involving the super secret realm of “black world” programs and operations. Mr. Tice attempted to bring these concerns to the House and Senate Intelligence Committees. Those attempts were rebuffed by the NSA and the chairmen of the intelligence committees themselves. To date, Russell Tice has not been allowed to address a full committee in closed session, or even a single member of congress, about the abuses in these SAP programs.