Sure it is, the government cannot act with impunity and violate it's own laws. If it killed Assange outside of it's laws, it would be murder, just as if any individual did it.
The US government does it all the time. Bush made it an art-form. They used excuses like "enemy combatant" to "it is not torture because we say so".. if they wanted Assange taken out then they could find some sort of excuse despite breaking every principle of the United States.. they have done it before. For a country that tries to project its democracy to the world and its freedoms, the US has a tendency to piss on those principles when ever it sees fit and make up a bunch of idiotic excuses to justify their illegal actions.
Question is.. what would it actually accomplish other than make the US look even more foolish and idiotic than it already is? Everyone would know that Assange's death would be related to the US, everyone would blame the US.
1.) The man has not broken any US laws, because his acts were not done in the US and last I looked US law did not apply outside US borders. How can he be a spy if he was not in the US when the supposed "spying" was done?
2.) His death would not stop the leaks or others for doing something similar. In fact it would more than likely make people even more determined to hit the US with leaks. There is already a new competing site that opened yesterday so this kind of exposing of government and big business is set to continue regardless of threats or murders. And frankly I think it is a good thing as a principle. If such sites expose illegalities by government and/or big business then I am all for it.
3.) What real damage has the leaks actually done other than a bit of pride and embarrassment? A list of "key sites" that most terrorists and enemies most likely knew of already? Making Hilary and a few ambassadors look like fools? Telling the truth about foreign leaders.. oh the shock!
I understand fully the US needs to act tough and all that, and especially the right wing fanatics, but in the real world.. what exactly has the US lost here with the leaks? Stuff that the "enemy" most likely already knew? wupti du..
In fact I would claim Assange and the PFC that stole the information in the first place, should be congratulated and rewarded by the US government for exposing a serious security threat within its own system and forcing a much needed review on who, how and where the information is shared. Banning removable media for one is a huge step forward.. why it was allowed in the first place baffles me.
The US intelligence community has grown insanely the last decade with more and more administration, and the results have not been mind boggling by any means. And all it took to hurt said massive bureaucracy system was a lone PFC with a grudge and a bunch of DVDs.