By JOSH GERSTEIN

The Justice Department has dropped its long-running criminal investigation of a lawyer who publicly admitted leaking information about President George W. Bush’s top-secret warrantless wiretapping program to The New York Times — disclosures that Bush vehemently denounced as a breach of national security. They also stoked a congressional debate about whether the government had overstepped its authority as it scrambled to respond to the Sept. 11 terror attacks.

The decision not to prosecute former Justice Department lawyer Thomas Tamm means it is unlikely that anyone will be charged for the disclosures that led to the Times’ Pulitzer Prize-winning story in December 2005, revealing that after the Sept. 11 attacks, Bush ordered the interception of certain phone calls and email messages into and out of the U.S. without a warrant — a move many lawyers contend violated the 1978 law governing intelligence-related wiretaps.

The petering out of the warrantless wiretapping leak investigation amounts to a low-profile and ambiguous conclusion to an episode that dominated the headlines in the second half of the Bush administration. While Washington is immersed in the latest round of WikiLeaks revelations and the investigation into new disclosures of a trove of government secrets, the dropped wiretapping investigation amounts to the final chapter of the most significant leak of the Bush era.

The Justice Department would not discuss the current status of the probe, which began in late 2005 after the Times story was published with a formal leak complaint from the National Security Agency. However, Tamm’s attorney, Paul Kemp, told POLITICO he and his client were informed “seven or eight months ago” that the investigation into Tamm was over.

The information was relayed during a meeting with the prosecutor handling the case, William Welch, Kemp said. The Justice Department recently issued Tamm a letter, confirming that the probe had concluded, the defense attorney said.

Prosecutors also appear to have lost interest in a former National Security Agency official who also publicly acknowledged being a source for the Times on the warrantless wiretapping story, Russell Tice. An attorney for Tice, Joshua Dratel, said it has been several years since prosecutors contacted him about the investigation.

“I have not heard anything from them in a very, very long time,” Dratel said Monday. “I haven’t been concerned about it in a long time. … I never thought [Tice] had anything to worry about.”

Asked about the apparent move to drop the inquiry, Dratel said: “I think it’s the right decision.”

Former federal prosecutor Victoria Toensing said the decision not to prosecute Tamm signals that the investigation is, in essence, dead.

“If the guy who came forward and said, ‘I admit it. I gave the information to The New York Times,’ is not going to be indicted, then no one is,” Toensing said. “It’s perplexing why this case wasn’t pursued. … I expect the Judiciary committees or somebody in Congress will pull someone in from the Justice Department and ask some tough questions about it.”

One factor that may have helped torpedo any prosecution is the numerous public claims that the warrantless wiretapping program was unlawful.

“No more illegal wiretapping of American citizens,” then-Sen. Barack Obama (D-Ill.) declared in August 2007. “No more ignoring the law when it is inconvenient. That is not who we are. And it is not what is necessary to defeat the terrorists.”

“I … never thought that I would see that a president would act in direct defiance of federal law by authorizing warrantless NSA surveillance of American citizens,” Eric Holder, Obama’s future attorney general, said in June 2008.

Since taking office, neither Obama nor Holder has repeated their previous statements that the program was illegal. At a Senate committee in 2009, Holder said, “I’m not sure I’d use the term illegal,” but added that he considered the early phase of the surveillance program “inconsistent with” and “in contravention of the law.”

Just last month, the Justice Department refused to say whether it stands by a May 2004 legal opinion which concluded that surveillance programs in effect at the time were lawful.

An early version of the surveillance program also produced a heated conflict between top Justice Department officials and the Bush White House in 2004. Deputy Attorney General James Comey concluded that an aspect of the program was illegal and refused to reauthorize it. Then-White House counsel Alberto Gonzales went to the bedside of ailing Attorney General John Ashcroft in an unsuccessful bid to get Ashcroft to override Comey’s position. The showdown led Comey, FBI Director Robert Mueller and Office of Legal Counsel chief Jack Goldsmith to threaten to resign.

Those kinds of doubts and disputes about the surveillance effort’s legality would complicate any leak prosecution and could have contributed to a decision not to indict Tamm or others, former federal prosecutor Peter Zeidenberg said.

“What leaps out to me is the fact that the program was arguably illegal, so while that does not provide a legal defense or immunity to the leaker, from a practical jury-appeal standpoint, which a seasoned prosecutor should consider, how appealing is the case going to be if they’re prosecuting government attorneys for disclosing the program but … the people who were doing the wiretapping don’t get prosecuted?” asked Zeidenberg, who was a prosecutor on the leak-related case against Bush White House aide Lewis Libby. “How would you like to be the prosecutor to get up there and make that argument?”

Asked about suggestions that the case may have been dropped because of doubts about whether the program Tamm and others discussed was legal, Toensing said: “That’s outrageous. … It’s certainly not per se illegal.”

Toensing said opponents of any prosecution were exaggerating the import of the program’s legality to a prosecution of those who leaked. “The legality of it is not for the jury to decide,” she said. “Any decent federal judge would make that not relevant.”

But Zeidenberg said such issues, including Obama’s and Holder’s public statements, were bound to influence the judge — and could affect a jury as well.

“It all goes to the atmospherics of the case,” Zeidenberg said.

Another possible reason for not prosecuting the leak is the continuing sensitivity of the technology and policies the National Security Agency uses to conduct surveillance. While the surveillance program was modified several times during the Bush administration, including after the Comey-Gonzales showdown, Congress passed legislation in 2008 that amounted to a legal blessing to continue at least some aspects of the monitoring regime, though with a new procedure for court review.

Lawyers close to the investigation noted there were never any indications that the Justice Department subpoenaed the authors of the Times article, James Risen and Eric Lichtblau. Such subpoenas could have come either during the Bush administration or the Obama era, but did not — even though Risen was called before a grand jury twice about classified information in some of his other work.

The Times’s wiretapping story fueled calls for prosecution not only of the leakers, but the Times as well.

At a press conference a few days after the Times story was published, Bush angrily denounced the leak. “My personal opinion is it was a shameful act for someone to disclose this very important program in a time of war. The fact that we’re discussing this program is helping the enemy,” he said. “It is a shameful act by somebody who has got secrets of the United States government and feels like they need to disclose them publicly.”

Bush also said he expected a thorough investigation. “There is a process that goes on inside the Justice Department about leaks, and I presume that process is moving forward,” the president said.

Tamm did not respond to several requests for comment for this article. After he left the Justice Department, he publicly revealed that he was a source for the Times and a focus of the FBI-led leak investigation in a December 2008 article in Newsweek magazine that many saw as an effort to get sympathetic treatment from the incoming Obama administration.

“I thought this [secret program] was something the other branches of the government — and the public — ought to know about. So they could decide: do they want this massive spying program to be taking place?” Tamm told Newsweek. He said he dropped the dime on the NSA program by calling the Times from a pay phone at a Metro station.

He maintains that he never had details of the secret program and did not disclose any classified documents.

Another suspect in the warrantless wiretapping leak, Thomas Drake, was indicted last year on charges of illegally keeping classified documents in his home and lying to investigators. However, those documents allegedly relate to a separate series of leaks about an NSA contracting dispute. Drake pleaded not guilty and faces a trial in June.

Prosecutors have also ended their inquiry into another official who was once a focus of the warrantless wiretapping leak investigation, former House Intelligence Committee staffer Diane Roark, according to her attorney. Roark’s home was searched in 2007, but she was never charged with any crime.

“Diane Roark has not been a subject of that investigation for a long time,” Roark’s lawyer. Nina Ginsberg said. “The government resolved any issue they had concerning her several years ago.”

CORRECTION: An earlier version of this article referred to Diane Roark as a former Senate Intelligence Committee staffer. She worked for the House Intelligence Committee.