I believe it's not illegal to publish the leaked material whether stolen or not as journalists do it all the time. One just cannot be involved in the stealing of the material. They at trying to get him on talking on the phone and saying do what you can or something trivial like that whilst talking to Chelsea Manning. They claim he helped Chelsea break a password but the odd thing is Assange has been technically locked up longer than Chelsea Manning was in gaol and who was then pardoned by Obama. Like him or hate him it's pretty gutless that Australian government seems to not have the spine to stand up for his rights.
