The Department of Justice announced 17 new charges against Wikileaks co-founder Julian Assange on Thursday, including a virtually unprecedented move to charge him with publishing classified material — a move that could pose challenges to First Amendment protections.

In a superseding indictment, a grand jury in Alexandria, Virginia, has accused Assange of breaking the law by inducing Army Pvt. Chelsea Manning to send him classified documents — and then publishing material that included the names of confidential sources who provided information to American diplomats.

The 17 counts were tacked on to a single count accusing Assange of conspiring with Manning to crack a Department of Defense password. Assange, who was taken out of the Equadorian embassy in London in April, is being held in a London jail for jumping bail on a sex charge and awaiting extradition to the United States.

The government says Manning provided Assange and WikiLeaks with databases containing about 90,000 Afghanistan War-related significant activity reports, 400,000 Iraq War-related reports, 800 Guantanamo Bay detainee assessment briefs, and 250,000 U.S. Department of State cables.

The material, which began to be published in 2010, made headlines across the world and shed light on U.S. government activities.

The decision to charge Assange in connection with publishing secrets crosses an important line. The U.S. government has never successfully prosecuted anyone other than a government employee for disseminating unlawfully leaked classified information, according to University of Chicago Law Prof. Geoffrey Stone, even though the Espionage Act has long been on the books.

Journalists publish classified material regularly, yet the government has opted not to prosecute a journalist — even when government officials have been deeply angered by the revelations of classified intelligence information.

"Today the government charged Julian Assange under the Espionage Act for encouraging sources to provide him truthful information and for publishing that information," Assange's attorney Barry J Pollack said in a statement. "The fig leaf that this is merely about alleged computer hacking has been removed. These unprecedented charges demonstrate the gravity of the threat the criminal prosecution of Julian Assange poses to all journalists in their endeavor to inform the public about actions that have been taken by the U.S. government."

In a briefing for reporters, Justice Department officials said they do not consider Assange a journalist, and they took pains to say they will not target journalists.

“The department takes seriously the role of journalists in our democracy,” Assistant Attorney General for National Security John Demers said.

Demers and other officials said they only charged Assange with publishing a narrow subset of material that included the names of confidential sources, including people who risked their lives talking to the U.S. government.

“Assange thereby is alleged to have created grave and imminent risk to their lives and liberty,” Demers said.

While that action by Assange and Wikileaks has long been criticized, press freedom advocates have worried that criminalizing the act of publishing opens the door for the government to charge journalists who make publishing decisions government officials don’t like.

For example, CIA officials were furious when The New York Times in 2015 published the true name of a longtime CIA counterterrorism official, Mike D’Andrea, who had been in charge of the agency’s targeted killing program. The Times said the move was justified because of his leadership role in one of the government’s most significant paramilitary programs and because his name was known to foreign governments and many others.

WikiLeaks, the anti-secrecy organization Assange founded, tweeted, “This is madness. It is the end of national security journalism and the first amendment.”

Edward Snowden, the former NSA contractor who leaked secrets and is now living in Moscow, tweeted, “The Department of Justice just declared war––not on Wikileaks, but on journalism itself. This is no longer about Julian Assange: This case will decide the future of media.”

Zachary Terwilliger, the U.S. attorney who brought the charges, told reporters that the United States “has not charged Assange for passively obtaining or receiving classified information.”

Rather, he said, Assange is charged “for his alleged complicity in illegal acts to obtain or receive voluminous databases of classified information.”

“Any government use of the Espionage Act to criminalize the receipt and publication of classified information poses a dire threat to journalists seeking to publish such information in the public interest, irrespective of the Justice Department’s assertion that Assange is not a journalist,” said Bruce Brown, executive director Reporters Committee for Freedom of the Press.

Manning is in jail in Alexandria, having refused to testify before the grand jury in the case.

After Assange helped Manning purloin classified documents, the superseding indictment charges, Assange published on WikiLeaks material “that contained the unredacted names of human sources who provided information to United States forces in Iraq and Afghanistan, and to U.S. State Department diplomats around the world. These human sources included local Afghans and Iraqis, journalists, religious leaders, human rights advocates, and political dissidents from repressive regimes.”

The indictment says that act “put the unredacted named human sources at a grave and imminent risk of serious physical harm and/or arbitrary detention.”

Asked by a reporter whether they could point to an example of a U.S. source who had been harmed by the publication, the Justice Department officials were unable to do so. But they said they were prepared to prove that the sources were at risk.