The CIA can get you anywhere, as can Mossad or pretty much any other agency. Heck, even Libya managed attacks in western countries. It's just that diplomatic repercussions or outright war are usually enough of a deterrent.

In this particular case, the US can't do anything about it. Obama said he won't use fighter jets to get Snowden. If he fails on even that concrete specific and understandable promise, then he can kiss a good deal of American influence in the world goodbye.