It is a crime to disclose classified information under the Espionage Act of 1917 (see 18 U.S. Code § 793, paragraph e). The Supreme Court upheld its constitutionality in Schenck vs. United States (1919). The Court ruled that "Words which, ordinarily and in many places, would be within the freedom of speech protected by the First Amendment may become subject to prohibition when of such a nature and used in such circumstances a to create a clear and present danger that they will bring about the substantive evils which Congress has a right to prevent." The First Amendment does not protect espionage.

The most famous prosecution under the Espionage Act was the Pentagon Papers case, New York Times vs. United States (1971), in which the Nixon administration attempted to stop the publication of a Department of Defense internal history of the Vietnam War. The Nixon administration lost the case and the New York Times (and others) published the history in full. Since the Pentagon Papers case, administrations have been generally reluctant to prosecute under the Espionage Act both because of the perceived difficulty of winning a conviction and because of general discomfort with the idea of suing the media for the content of what they publish.

The Pentagon Papers case is, however, a poor guide to Espionage Act prosecutions. The administration sought to prevent the Times from publishing, not bring criminal charges against it for what it had already published. The Court ruled that such attempts at "prior restraint" must meet a higher standard, which the Nixon administration failed to do regarding the Pentagon Papers -- which was, after all, just an internal history, not a record of ongoing operations. The Court did not invalidate the Espionage Act, nor did the ruling acquit the New York Times.

In fact, Supreme Court Justice Byron White, in his concurrence, practically invited the administration to pursue prosecution against the New York Times after the publication was completed. The "failure by the Government to justify prior restraints does not measure its constitutional entitlement to a conviction for criminal publication," he wrote, "I would have no difficulty in sustaining convictions under these sections on facts that would not justify ... prior restraint." This was in 1971.

Much more recently, the New York Times (among other media outlets) has a well-established habit of disclosing classified information. In 2005 it disclosed the existence of the National Security Agency's terrorist surveillance program. In 2006 it disclosed the U.S.'s efforts to track terrorists' financial transactions through bank records. In July 2010 it was complicit in WikiLeaks's disclosure of some 92,000 U.S. military documents related to the Afghan War. In October, it helped publicize WikiLeaks's access to 400,000 U.S. military documents related to the Iraq War. And in November it helped with the disclosure of 250,000 diplomatic cables.

Oct. 25, 2005: Citing lawyers connected to the case, The New York Times reports that Lewis Libby, Vice President Dick Cheney's chief of staff, first learned about Plame from a conversation with Cheney in the weeks before her identity became public in 2003. Libby's notes from that conversation, which took place June 12, 2003, contradict Libby's testimony to a federal grand jury that he first learned about Plame from journalists, lawyers told the paper. The previously undisclosed notes are now in the possession of prosecutors.

Oct. 28, 2005: Vice presidential adviser I. Lewis Libby is indicted on obstruction of justice, false statement and perjury charges in the CIA leak case. Libby resigns as Vice President Cheney's chief of staff.

Nov. 3, 2005: Libby pleads not guilty in federal court to the five-count indictment against him.

Nov. 15, 2005: Washington Post editor Bob Woodward testifies that a "senior administration official" told him about Valerie Plame and her job at the CIA nearly a month before she was first named in Robert Novak's column. The revelation would make the source, who Woodward refused to identify, the first official to reveal Plame's identity to a reporter.

April 26, 2006: Presidential adviser Karl Rove testifies for a fifth time before a grand jury. Fitzgerald says he is investigating whether Rove lied or obstructed justice in failing to initially disclose his conversation with Time magazine reporter Matt Cooper. Rove blamed a faulty memory.

June 13, 2006: A lawyer for Rove says his client has been informed by prosecutors he won't be charged with any crimes in the investigation, ending months of speculation.

January 6, 2007: Libby's criminal trial begins.

February 21, 2007: Jury receives case for deliberation.

March 6, 2007: Jury returns guilty verdict on four of five counts, convicting Libby of obstruction, perjury and lying to the FBI.

June 5, 2007: Libby is sentenced to 30 months in prison and fined $250,000.

June 14, 2007: U.S. District Judge Reggie Walton denies request to delay Libby's sentence.

July 2, 2007: A federal appeals court rejects Libby's request to remain free on bail while pursuing appeals -- meaning Libby would likely have to report to prison soon. Hours later, President Bush commutes Libby's prison sentence, leaving the $250,000 fine and two years probation intact. "I respect the jury's verdict," Bush says in a statement. "But I have concluded that the prison sentence given to Mr. Libby is excessive."

As for Mr. Assange, I thought the government's lack of prosecution of the NY Times or Washington Post in the Pentagon Papers publication meant something, but perhaps not If the act is applied, he could be prosecuted, provided he were extradited. Now the worthiness of extradition is another can of worms entirely, to me. The cat's out of the bag, and we can't get it back in. At the end of the day, even if he COULD be tried, it may be a waste. This isn't your old-fashioned cold war espionage case in my nonlawyer/nonprosecutor opinion.