What we're talking about is an international game of brinksmanship.
Illegality is a relative proposition. There are scarce few international laws that govern anything and even fewer international laws with teeth. Each individual nation has laws against spying, but given the propensity to avoid an international incident, I tend to think that spies who are discovered are either tortured or returned to their home countries. Since the laws of one country do not extend beyond their borders, it's difficult to enforce ones sovereignty in a different country, or to exert ones own authority over another nation-state's actor.
This is all just very murky, but the concept of illegality is relative at best in this instance.
The specific details of the NSA's (or any foreign intelligence service of any nation) intelligence gathering would be news, but the fact the NSA (or any foreign intelligence service of any nation) actually gathers intelligence outside of its home nation, quite often in violation of the laws of the places from which the intelligence is gathered, really isn't news.
I mean, that's the whole point of foreign intelligence services.