The Central Intelligence Agency is poised to get involved in domestic surveillance and investigations in ways that are unprecedented in its history.
The CIA's intelligence gathering has long been kept as separate as possible from domestic law enforcement, which is bound by strict evidence-gathering rules and legal safeguards protecting the rights of those investigated.
But as the nation girds itself against global terrorism carried out on American soil, the barriers between covert, stealthy intelligence and by-the-book domestic law enforcement investigations are beginning to melt.
Suddenly, for instance, the CIA will now have access to testimony collected by federal grand juries.
And the CIA, FBI, and other federal agencies are, for the first time, being allowed to share vast amounts of information ranging from phone records and credit cards statements to profiles of suspected terrorists.
These shrinking restraints come as new antiterrorism legislation adopted this fall grants the FBI far broader wiretapping and other investigative powers.
And while many see the new cooperation as essential in combating the enormous threat, for others it raises civil-liberties concerns - and resurrects dark memories of CIA monitoring of domestic groups, including 1970s antiwar protesters.
Those domestic intrusions drove Congress and the president to tighten restrictions dating back to the 1947 creation of the CIA that bar the agency from any "domestic police function."
"Traditionally, there's been a sharp demarcation between FBI and CIA turf ... but now there's more ambiguity," says Loch Johnson, author of "America's Secret Power: The CIA in a Democratic Society."
One of the most-significant changes is the CIA and other government agencies' new access to one of the most powerful domestic investigative tools - federal grand-jury proceedings - under the USA Patriot Act, which passed in the wake of Sept. 11. Now, if any grand-jury investigation involves matters of "foreign intelligence or counterintelligence" its fruits may be shared with relevant federal agencies, the statute reads.
"That's a big change in criminal law," notes Robert Davis, founder of the University of Mississippi's Journal of National Security Law.
Critics worry that "foreign intelligence" information is a very broad category that extends far beyond just fighting terrorism. They also worry the information flow won't just be one way. Instead, the CIA may eventually suggest certain avenues for investigation.
Defenders of the change argue prosecutors will be zealous about defending their grand-jury proceedings from outside interference.
What really worries critics is the CIA's past history of domestic operations. In the 1960s and '70s, for instance, Operation CHAOS included CIA involvement in spying on US citizens including antiwar protesters, black militant groups and even congressmen.
President Nixon's White House encouraged these activities, convinced that foreign powers stood behind anti-war radicals.
Yet advocates of the changes say the present threats on American soil differ significantly from the domestic snooping conducted by the Nixon administration.
In fact, supporters point out that drastic government measures - such as Abraham Lincoln's suspension of habeas corpus during the Civil War - have typically been temporary. Indeed, the most-controversial elements of the USA Patriot Act do eventually expire.
IN the meantime, the stepped-up cooperation is crucial, says ex-Director Gates, who argues the relevant historical parallel is not Operation CHAOS but Pearl Harbor.
In 1941 - as in 2001 - "disparate government agencies had bits of information" that pointed to an attack.
"But there was no single agency to pull everything together in a coherent analysis of the threat," Gates says.
The new information sharing is the only way to prepare against new attacks. The USA Patriot act allows the CIA, FBI, the Border Patrol, and the Immigration and Naturalization Service to share information broadly. And it's likely to lead to FBI and CIA agents working closely together here in the US.
This greater cooperation comes at a time of significantly increased federal investigation powers. For instance, under the PATRIOT act, law enforcement can now more easily conduct secret searches of homes and businesses, while a change to the Foreign Intelligence Surveillance Act makes it easier for law enforcement to obtain wiretaps.
Such activity may help prevent future terrorist acts. But there is also concern that it will lead to a blending of the intelligence and law-enforcement cultures.
Yet there are hints it won't be so easy for the two agencies to work together, given the history of antagonism between the two and the CIA's reluctance to repeat its past mistakes.
Somehow, experts say, the agencies must strike a tricky balance. "The concept of keeping them separate makes good sense in general," says University of Virginia law professor John Norton Moore. But after Sept. 11, "it's inconceivable not to have the two talking to each other."