Earlier this month, federal prosecutors filed a formal criminal complaint against Edward Snowden charging him with three felonies for leaking information about the National Security Agency's surveillance programs to Glenn Greenwald at the Guardian and Barton Gellman at the Washington Post. Two of those charges were filed under the 1917 Espionage Act.

Snowden is the seventh person the Obama administration has charged with violating the Espionage Act for leaking information to the press. Prior to 2008, only three other people had been charged with felonies under the Espionage Act for leaking documents.

Indeed, the first time the Espionage Act was applied to a whistleblower was in the case of Daniel Ellsberg, who leaked the Pentagon Papers to the New York Times in 1971.

This month marks the 42nd anniversary of the Times' publication of the first excerpts of the Pentagon Papers.

I serve on the board of directors of the Freedom of the Press Foundation with both Greenwald and Ellsberg, and minutes after news broke about Snowden's charges our board received an email from Ellsberg. It was short and to the point: "Same charges as against me, 40 years ago, except (so far) for conspiracy."

Ellsberg predicted, accurately, that Snowden wouldn't be charged with "espionage" per se, but rather with a violation of one specific part of the Espionage Act, 18 U.S.C. 793 (d). "Other parts of 792, 793 and 794 deal with real espionage; paragraph 793(d) could too, potentially, but has been used almost exclusively not for espionage but for unauthorized disclosures of classified information, starting with me in 1971, and all of Obama's prior prosecutions of leaks," Ellsberg wrote.

In the email, Ellsberg noted that the application of the Espionage Act to himself, Snowden, Bradley Manning and others is significant because the Act's original intent focused on "secretly conveying defense information to a foreign power, especially an enemy in wartime, with intent to help that power or harm the U.S."

On this point, James Goodale, the general counsel for the New York Times during the Pentagon Papers case in 1971, argues in his new book, "Obama apparently cannot distinguish between communicating information to the enemy and communicating information to the press. The former is espionage, the latter is not."

Indeed, the recently revealed "Insider Threat" program, which the Obama administration implemented after Bradley Manning handed over hundreds of thousands of documents to WikiLeaks, is perhaps the most troubling illustration of this fact. Marisa Taylor and Jonathan S. Landay of McClatchy report that under the program, "Leaks to the media are equated with espionage." They call the program "a government-wide crackdown on security threats that requires federal employees to keep closer tabs on their co-workers and exhorts managers to punish those who fail to report their suspicions."

This belief that leaks to the media are akin to leaks to an enemy state helps explain recent incursions on press freedom by the Obama Justice Department. These have included secret subpoenas of journalists' phone records and their characterization of Fox News journalist James Rosen as aiding and abetting in the leaks that he eventually published. In these cases, journalists have not yet been charged with anything but the Justice Department's actions have already had a chilling effect on journalists and their sources.

Scott Bomboy of the National Constitution Center reports that the current charges against Snowden carry a 30-year prison term, but that additional charges may be added as the investigation continues. And, he notes, "Section 794 of the [Espionage Act] contains the death penalty as possible punishment for giving information to the enemy during wartime."

Many media pundits and politicians are already wondering aloud if Snowden has provided NSA documents (knowingly or not) to either the Chinese or the Russians, though there is no evidence he has done either. In fact, he has steadfastly denied this.

The legacy of the Espionage Act, and especially its recent application to leaks and the press, is a troubled one. Not long after the Espionage Act was put in place, it was used three times against peaceful anti-war protesters: Charles Schenck, Eugene Debs and Jacob Frohwerk (Frohwerk was a columnist for a Missouri newspaper). Trevor Timm writes in the Atlantic that "Together, the trio of rulings did more damage to [the] First Amendment [than] any othercase in the 20th century."

Today, lawmakers like Peter King and journalists like David Gregory seem ready to extend the Espionage Act charges facing Snowden to Glenn Greenwald, the journalist who published Snowden's leaks.

In response to this, Erik Wemple has outlined what it would take to charge Greenwald under the Act. He finds it wouldn't be easy, but it should be troubling that so many people are even suggesting it. "Reading through the opinions and scholarly work on the Espionage Act reveals how carefully this country's finest legal minds have sought to protect press freedoms vis-a-vis our precious national security interests," Wemple writes. "Stunning to behold how carelessly some commentators would trample it all."

In an NPR interview this month, Benjamin Wittes of the Brookings Institution argued "the problems with the Espionage Act are that it is hopelessly broad." Greenwald echoed this sentiment in the Guardian, suggesting it was that vagueness that made administrations before Obama's leery of using it. Charles Pierce has called for its repeal, describing it as a "foul relic of a foul time […] employed to quash dissent during World War I, and then repurposed for the Red Scare."

The First Amendment and press freedom questions that haunt the Espionage Act are particularly important right now. Changes in media and technology have put the tools of journalism and media making in the hands of more and more people, challenging old assumptions about who is a journalist and how journalism is done. Increasingly, independent journalists, nonprofit news outlets and citizens are playing critical roles in newsgathering and reporting on the most important issues of our time.

Unlike Greenwald or Neil Sheehan, the New York Times journalist who first published the Pentagon Papers, these independent and citizen journalists don't have the resources, legal or financial, of major newsrooms to support them. As such, they are more at risk than ever. In this moment, an overly broad law like the Espionage Act can become a dangerous tool to silence and suppress both political dissent and rigorous journalism. Indeed, history has shown that it already has.