This might be my perception being biased from what media is reporting about.
But how I see it, here in Germany it is usually reported in media like:
"Spy [Name] was convicted of having transfered [SensitiveData] to [SecretService] of [State]. This means [Impact]. He will now face [JudicialMeasures]"
But while I understand that such activity can't be kept unpunished, as otherwise you had nothing to loose if you just hoarded any sensitive data you ever had access to.... just in case. I still don't understand why the focus is on punishing the spy, rather than the client state. I mean the spy acts either because he has gains from it, or even worse, someone holds information to blackmail him into making use of his access to specific data. So by punishing him for doing it, you got rid of a single person that was willing to execute this activity, but it is safe to assume that the client has still the same amount of interest in getting access to sensitive data and will most likely try to find another channel to obtain such data. And by rarely, if at all reacting politically on these attempts, as long they are not getting revealed en mass, I can't see how taking measures against individuals has any real impact at all, considering that not rarely it is foreign states financing the acquisition of such data, and with such resources, they probably will always be able to find others be willing to do that job, given the right pressure/payment. So I don't understand the rationale behind this.
So my question is: Is espionage internationally tolerated or, if not, what are political measures being taken to prevent or at least protect against it?