Journalists, First Amendment watchdogs and government transparency advocates reacted with outrage Monday to the revelation that the Justice Department had investigated the newsgathering activities of a Fox News reporter as a potential crime in a probe of classified leaks.

Critics said the government’s suggestion that James Rosen, Fox News’s chief Washington correspondent, was a “co-conspirator” for soliciting classified information threatened to criminalize press freedoms protected by the First Amendment. Others also suggested that the Justice Department’s claim in pursuing an alleged leak from the State Department was little more than pretext to seize his e-mails to build their case against the suspected leaker.

“It is downright chilling,” Fox News executive Michael Clemente said in a statement. “We will unequivocally defend [Rosen’s] right to operate as a member of what up until now has always been a free press.”

Steven Aftergood, director of the Project on Government Secrecy at the Federation of American Scientists, said, “Asking for information has never been deemed a crime.”

The reactions followed a Washington Post report on the inner workings of a Justice Department investigation into a possible leak of classified information about North Korea.

The case centers on Stephen Jin-Woo Kim, a former State Department arms expert accused of passing details to Rosen from a classified report within hours of its release to a small circle within the intelligence community. Investigators also targeted Rosen, calling him a co-conspirator in an affidavit seeking a search warrant for Rosen’s personal e-mails.

In the affidavit, FBI agent Reginald Reyes said Rosen “asked, solicited and encouraged Mr. Kim to disclose sensitive United States internal documents and intelligence information.” He added, “The reporter did so by employing flattery and playing to Mr. Kim’s vanity and ego.”

That detail particularly irked media lawyers and transparency experts, who said the Justice Department had crossed a line by equating routine reporting practices with possible criminal activity.

“Neither flattery nor an insistent tone rises to the level of a criminal offense,” Aftergood said.

Investigators pulled Rosen’s security badge records, phone logs and his personal e-mails, but they never charged him with a crime. No reporter has ever been prosecuted for seeking classified information.

Kim was accused in 2010 of disclosing national defense information; his trial could begin in 2014.

In response to questions about how Rosen was characterized in the affidavit, the Justice Department said in a statement Monday: “Saying that there is probable cause to believe that someone has committed a crime and charging the person with that crime are two different things.”

“No reporter has been charged in this case,” the statement added. “And, at this time we do not anticipate bringing additional charges against anyone.”

The investigation brought another controversy to the doorstep of the White House, where press secretary Jay Carney on Monday was besieged during his daily briefing with questions on whether President Obama believes it is ever a crime for reporters to solicit information from a source.

The Obama administration has pursued more leak investigations under the 1917 Espionage Act than all previous administrations combined; it was criticized last week by the Associated Press for a sweeping search of the news agency’s phone records as part of one ongoing probe. The case against Kim does not include allegations of spying or that he gave any documents to the media. It appears to charge him for having conversations with reporters, something his attorneys have said was part of his job and part of the normal course of business in Washington.

Citing the ongoing criminal investigation, Carney refused to answer most questions about the Kim case. He said that the president “believes very strongly in the need for reporters to be able to pursue investigative journalism” but that he “also has to be mindful of the need to protect classified information because of our national security interests.”

First Amendment advocates are closely watching whether the government will prosecute the anti-secrecy group WikiLeaks as a co-conspirator in the case of Army Pfc. Bradley Manning. The case, advocates say, could set a dangerous precedent that applies to mainstream media outlets and potentially criminalizes the practice of investigative journalism. Manning, who is facing a court-martial in connection with the leaking of 700,000 documents and other materials to WikiLeaks, pleaded guilty this year.

Attorney General Eric H. Holder Jr. told the House Judiciary Committee last week that prosecuting the press for disclosing classified material is not “wise policy.”

“The focus should be on those people who break their oath and put the American people at risk, not the reporters who gather the information,” he said in response to questions about the investigation involving the AP, which reported on a foiled plot involving the al-Qaeda affiliate in Yemen.

The office of the U.S. attorney for the District of Columbia, Ronald Machen, who is involved in both the AP and Kim cases, said it had “exhausted all non-media alternatives for collecting this evidence” before seeking Rosen’s personal e-mails.

A U.S. magistrate judge, Alan Kay, signed off on the search for two days’ worth of Rosen’s personal e-mails and all of his correspondence with Kim in May 2010. The warrant was unsealed in 2011, but a Fox executive confirmed that the network was not aware of the characterization of Rosen as a co-conspirator until Monday.

The Justice Department was not required to inform Rosen that his personal e-mails would be seized, according to an opinion by U.S. District Judge Royce C. Lamberth in 2010.

Brit Hume, a senior political analyst on Fox, said on the air Monday that the Justice Department had crossed a “clear bright line” when it seized the records on what he called “the pretext that this activity was criminal.”

“The Obama-Holder Justice Department is now prepared to treat the ordinary newsgathering activities of reporters, trying to seek information from government officials, as a possible crime,” he said. “I can’t think of a case in which that’s happened before.”

Scott Wilson contributed to this report.