On the day the World Trade Center came crashing down, historian Philip Melanson was finishing up the research for Secret Service (Carroll & Graf, Oct.), his history of the agency charged with protecting the president and other government officials. A few days later, when he contacted archivists for the agency, Melanson immediately noticed a change."They had tightened up incredibly," he said. "There was almost a complete blackout. I couldn't even get an organizational chart."

Prying government documents away from tight-fisted archivists has always been a frustrating task. Yet it's also proven a major source of content for the publishing industry, especially since the end of the Cold War. Using files obtained under the Freedom of Information Act (FOIA), authors have published books uncovering Nixon's attempts to deport John Lennon, confirming the probable guilt of alleged spy Alger Hiss and exposing J. Edgar Hoover's secret war on Albert Einstein. Sporting the tagline "Based on recently declassified documents," these books produce headlines and talk-show spots for their authors; they also generate a steady if not lucrative income for publishers.

"They've always been a big part of my list, and of our backlist in general," said Philip Turner, executive editor at Carroll & Graf. "We've probably published 10 books in the last 10 years that could not have been written without FOIA requests."

But that well is drying up. In an attempt to strengthen national security after September 11, the Bush administration moved swiftly to slow or even cut off the flow of information from all areas of government. Last October, Attorney General John Ashcroft issued a secret memo directing federal agencies to resist as much as possible any FOIA requests for government documents. ("You can be assured the Department of Justice will defend your decisions," Ashcroft wrote.) Last November, Bush issued an executive order sealing Ronald Reagan's presidential records, which had been scheduled for release. And now, his administration is fighting to keep "homeland security" files safely locked away.

All of this has had what Turner called a "chilling effect" on authors, editors and agents. "There's a lot of concern among my authors," said Turner. "The books I'm publishing this year were mostly researched before 9/11. But the books I have contracted for next year and the year after are the ones that could be really hurt."

Jack Macrae, who under his Henry Holt imprint recently published Greg Herken's book about Robert Oppenheimer, Brotherhood of the Bomb, thinks the new policies might discourage publishers from considering FOIA titles. "These books will take even longer to write and they'll be more expensive," said Macrae. "Publishers will have a lot of good business reasons for skipping these books."

There has been some successful resistance to the Bush clampdown. Last year, a loosely organized coalition of historians, journalists and open government advocates filed a lawsuit (American Historical Association v. National Archives) that resulted in the release of 68,000 pages of Reagan's presidential records that Bush had sought to keep sealed. But even that effort was only a partial win: at least 150 pages of documents remain boxed up due to national security concerns.

Additionally, many of the administration's other policies, such as Ashcroft's FOIA directive, are technically within the law and unlikely to be overturned by the courts. With those roadblocks in place, authors might have no choice but to avoid subjects for which they know they can't obtain documents, said Susan Rabbiner, an agent for many historian authors. "I think it's likely that some books will be postponed until new policies come in, or even a new administration," she said.