I’m not sure the espionage case is quite that clear-cut. Assange runs a website that expressly solicits Americans with high clearance to steal and transmit classified information into their hands. That sounds like espionage to me.
Whether they requested this specific information beforehand doesn’t seem relevant when they have issued a general request for any and all classified information.
Actually, he runs a website that encourages anyone, anywhere, to send any otherwise publicly unavailable documents. The first stories WikiLeaks carried had nothing to do with America, and most of the releases haven't been related to our government. We just have the biggest and most famous ones.
My favorite was the Australian Internet censorship list. The Australian government blocks various web sites, supposedly only those related to child pornography and terrorism. The list was leaked, exposing that they'd blocked many other sites too, including some Christian sites. The hilarious part was the Australian government saying the leaked list was fake, but threatening prosecution for anyone caught distributing it.
Its a legal grey area, to be sure. But why is he still breathing? We used to know how to handle business.