The local FBI office has used new and far-reaching powers to persuade Strip casinos to turn over personal information of certain visitors for use in terrorism investigations.

The FBI frequently has issued so-called national security letters, or NSLs, said Dave Staretz, chief division counsel for the bureau's Las Vegas office.

Through the use of NSLs, the FBI can get information including telephone, credit card and Internet records without search warrants or court approval. The information can be stored in federal databases for an unlimited time and shared with other government agencies, according to federal law.

The issuance of NSLs to casinos is a particularly sensitive issue because of the premium that resorts put on guest privacy. Resorts aren't obligated to turn over even hotel registration records to authorities without a court order, said former Clark County Sheriff Jerry Keller, who until May was vice president of security for Wynn Las Vegas. One of the few requirements of guests is that they show identification to hotels upon request.

The detailed information sought through NSLs serves as a reminder that what happens here doesn't always stay here. The secret letters add to the misgivings of civil rights groups that contend the FBI has used anti-terrorism tools for matters unrelated to national security.

The ACLU bristled when the FBI used the Patriot Act to obtain financial records in the public corruption investigation of strip club owner Michael Galardi and four former Clark County commissioners.

Ellen Knowlton, who until February headed Las Vegas' FBI office, said NSLs are a "bona fide technique" of gathering information from businesses, including resorts, for terrorism investigations.

But Lisa Graves, senior counsel for legislative strategy for the American Civil Liberties Union, said NSLs threaten privacy rights and lack safeguards to prevent abuse.

"The government's position is literally any time you turn over information to a third party that you have no privacy in that information," Graves said. "Their power is unchecked."

Senate Minority Leader Harry Reid, D-Nev., said Thursday he was concerned that FBI agents "are not required to have any evidence that the records sought are connected to a terrorist."

In a related matter, a federal judge in Detroit earlier this month ruled unconstitutional a federal government program that allows the National Security Agency to intercept international phone calls and e-mails of suspected terrorists.

National security letters, which were created in the 1970s primarily as a tool to expose foreign agents, have experienced a resurgence during the war on terror.

The Patriot Act allows the FBI to use NSLs as a tool of domestic surveillance to obtain any information "relevant" to an international terrorism or espionage investigation. The Patriot Act places no limits on the amount of data that can be requested.

Unlike grand jury subpoenas, which require court oversight, NSLs are distributed through local FBI offices with final approval from the special agent in charge of the office.

Nationwide, the FBI distributed 9,254 NSLs last year, according to Justice Department figures.

Subjects of NSLs never are informed that their records have been turned over to the government.

The ACLU's Graves said the secret letters are excuses to delve into the private lives of people not accused of crimes.

But Staretz said NSLs are used only in pending investigations.

"If we want to prevent terrorism, we've got to have information," Staretz said. "If there's a lawful demand of information, at some point you have to comply with it."

Staretz declined to provide details about the number of people who have been the subject of NSLs, to which hotel-casinos they have been sent and how much information has been requested.

FBI Assistant Director John Miller said in an interview that the debate over the use of NSLs is "ludicrous."

"Why in a terrorism case, given the stakes at hand, should investigators be required to jump through more hoops than you'd need to when going after a marijuana farm or Medicaid fraud?" Miller asked.

The only legal challenges to NSLs have been filed by the ACLU on behalf of an anonymous Internet service provider and a group of Connecticut librarians who questioned the constitutionality of the letters.

In the library case, a federal judge granted an injunction that allowed the librarians to reveal receipt of the letters.

The federal government appealed the ruling, and the ACLU has gone back to court to argue again that the gag provision violates the First Amendment.

Dave Shepherd, who resigned as director of security at The Venetian earlier this month, told the Review-Journal that the resort has "cooperated at different times" when the government has asked for customer information through means including NSLs.

Shepherd, a former FBI agent, said his hotel willingly complied with the requests.

"We don't question it. We respond," Shepherd said. "How would you like to be the person who didn't cooperate and something happens?"

Knowlton said NSLs are only one way for authorities to access information about hotel guests.

Knowlton and Staretz said the FBI relied on voluntary disclosure of data from casinos to learn about visitors to Las Vegas around New Year's Eve 2003 when the city was mentioned as a possible terrorist target.

"We destroyed those records some time before I left," Knowlton said.

It is unclear whether the Justice Department still has the information in its files.

Bruce Gebhardt, senior vice president of global security for MGM Mirage and former second-in-command at the FBI, defended the bureau's use of the secret letters.

"The FBI is not cavalier in sending out NSLs," Gebhardt said. "They're usually very specific. It's not a shotgun approach."

Gebhardt said he was not aware of NSLs being sent to MGM Mirage hotels in the 18 months he has worked for the company.

Juliette Kayyem, a lecturer at Harvard University and former member of the National Commission on Terrorism, said NSLs are an invasive and ineffective way to obtain information.

"They look at private, legal activities," Kayyem said. "We're left to rely on the good faith of FBI agents who basically know these fishing expeditions tend to be a waste of time."

Kayyem said the fact that NSLs are being issued without court approval is a sign that the FBI is conducting "much larger searches" than they acknowledge.

The FBI and gaming industry officials met late last year to discuss the privacy implications of NSLs. Before the meeting, American Gaming Association Chairman Frank Fahrenkopf released a statement in which he called the letters "an unacceptable intrusion on the privacy of our customers."

But less than a month later, after the meeting with the FBI, Fahrenkopf issued a second statement with a different point of view.

"The security of our customers, employees, and nation are of utmost importance to the commercial casino industry, and the industry has long been a willing partner ... in the ongoing war on terrorism," Fahrenkopf said.

Holly Thomsen, a spokeswoman for the gaming association, said in an e-mail last month that her group no longer would comment on privacy issues.

Kayyem said the highly regulated casino industry is put in a difficult position when confronted with the letters.

"They have no interest in getting on the bad side of law enforcement, but they're also faced with the expectation their clients have of privacy," Kayyem said.

Las Vegas native Jeff Jonas, chief scientist with IBM's Entity Analytic Solutions, said new technology can improve protection of customer privacy.

Jonas invented a technique currently being used by some government agencies that makes customer data anonymous by configuring it in such a way that only a computer can read it.

"It produces an ability for the government with a watch list and a casino with sensitive customer data to analyze data so that neither can learn about what the other has, only what they have in common," Jonas said.

William Thompson, a gaming professor at the University of Nevada, Las Vegas, said hotel-casinos probably won't be bothered by the information demands unless it begins to hurt business.

"If (the FBI) is too intrusive and casinos notice that good players are being lost to casinos in Saskatchewan, I suspect the appropriate howls will be heard," Thompson said.