I see. However, to use the analogy, there's no camera. There was no innocent acquisition of the material. The tape is stolen with the express intent of using its contents. Tape is given to someone else - who uses its contents. More so, the secondary person (in this case, WikiLeaks), *knows* the tape is stolen, as there is no other way to obtain it. In this case, WikiLeaks isn't an innocent 3rd party - they are an accessory to theft. The only thing preventing them from being treated as such is that they aren't in the U.S.
We can argue the value of the material being leaked, but I think there's much less of a case to say that WikiLeaks is a "3rd party". They knew exactly what they were being handed, and why.