Justice Department officials are delving into an online chat log between Assange and the analyst, Pfc. Bradley Manning, who is suspected of leaking the information to Assange.
Whether Assange in any way attempted to encourage or help the analyst extract classified military and State Department files from a Government computer system, is what the Justice Department are trying to find out, right now. If they can find any kind of evidence to suggest that this did in fact take place, then they just might be able to build a conspiracy case against him.
So if the Espionage Act of 1917 does not fit the bill, perhaps the idea of conspiracy charges could be more fruitful. If not of course there is always the Computer Fraud and Abuse Act of 1986 to consider. Either way, it looks like the U.S. is not giving up anytime soon in its quests to find some crime that they can charge Julian Assange with.