The Bush administration, Wells argues, has been unable to resist using a vague national security rationale for withholding information that might prove embarrassing to its policy decisions. She cites documents that could shed light on what Bush truly knew about the absence of weapons of mass destruction in Iraq before invading that nation, or what he knew about torture of prisoners at the Abu Ghraib detention center, as examples.

"In addition to relaxing classification criteria after the Sept. 11, 2001, terrorist attacks, the Bush administration encouraged officials to withhold 'sensitive but unclassified information,' which arguably should be disclosed under FOIA," Wells says. "The administration further lobbied heavily for the Homeland Security Act of 2002, which specifically exempts 'critical infrastructure information' from FOIA disclosure." Because so much of the nation's infrastructure is privately owned, she adds, the exemption has much potential for abuse.

Like previous presidents, both Republican and Democrat, George W. Bush determines executive branch classification policy through "executive order," a form of presidential fiat that does not need approval by Congress -- and which courts are loathe to question. As a result, deciding what information is off-limits to the citizenry is a process that escapes the checks and balances built into the U.S. Constitution by the framers.

In an era defined, rightly or wrongly, by a "war on terrorism," government's withholding of documents is likely to increase, Wells fears. "Given human nature, over-classification and the tilt toward secrecy is an understandable phenomenon," Wells says. "All executive orders instruct classifiers to gauge the type of threat information poses to national security when determining whether, and at what level, to classify information. With the current understanding of 'national security' encompassing all potential threats to U.S. interests, the classification process does not just involve identification of concrete threats."

Officials in places such as the Pentagon, she adds, know they will never incur the disfavor of their superiors by withholding too much information from public view.

Wells provides poignant examples from the second half of the last century to illustrate the phenomenon. After the close of World War II, for instance, the U.S. government secretly participated in the forced repatriation of anti-Communist Russians, refusing more than 20 years later to declassify its files on the subject. In the 1960s, executive officials maintained secrecy regarding the government's policies in Vietnam and its war in Cambodia. The reason was not to protect soldiers but to boost public support and prevent revelations of embarrassing failures. Similarly, the Nixon administration hid its secret support of Pakistan during the 1971 India-Pakistan War to avoid upsetting the American public.