Actually, it is not clear that publishing classified information and/or documents is illegal. The New York Times does it with some frequency. For example, look at the
Pentagon Papers.
More recent examples include the
New York Times Writer that keeps leaking information about Flame and Stuxnet.
Its clear that Julian has published things that have embarrassed the US... Then again, so has the New York Times and many other news organizations.
If the US Attorney General allows the New York Times to publish classified information with impunity, it would seem to be inconsistent to attempt to prosecute a foreign national residing in a foreign country for doing the same thing...
Uno