>If you don't want to answer about the chance of conviction, what do you wager the chances of a prosecutor simply bringing a case to a German court are?
And rightfully so! I think forcibly kidnapping someone on the streets of Italy is different than an allied intelligence agencies dropping each other tips about leakers.
Whether allied or not, foreign intelligence agencies spying on German citizens in Germany are unlawful and occasional "help" in the form of informal tips should not make them above the law. NSA should not get preferential treatment over CIA in EU courts and US agencies in general should not get preferential treatment over say China.
I'm talking about what is, not what should be in some perfect world we have no practical way of achieving.
Intelligence agencies are above the law not because they offer tips to each other, but because they have the resources and practice to be careful and not to leave enough evidence to be used to charge anyone.
There's also something fundamental to the nature of dealing in information - you can send anonymous tips, or suggest something while maintaining plausible deniability. I'm sure the source here didn't hand German intel a notarized letter saying "I'm John Doe of the CIA and we've been tapping Der Spiegel phones and this dude's definitely their source on the inside".
Spooks are not gods, it's public's attitude towards them that makes them god-like. German gov't could have started investigation and at least informed Spiegel. They might have found some leads. If not, at least security audit would have made them more aware of threats. Surely the same (hypothetical) entrypoints that NSA/CIA used, could have been used by other organizations or governments. Spiegel covers a lot of international news and certainly has a lot of sources around the world to protect.
Certainly not gods, but immensely powerful organizations with varying moral frameworks and political interests all acting without the convenience of a global system of legal and moral guidance that you and I operate in. Have you ever had to hassle about what's fair to put in a lease? Probably not, since the legal system provides for a pretty rigid API between landlords and tenants. The world we live in is a large series of such APIs, which are constantly and modified via our political and legal systems. The space ICs operate in simply does not have such rules nor anyone to enforce them.
In a world where information is power and without a justice enforcer more powerful than the actors, an unknown leaker is significantly more of a threat than an allied IC. An ally will keep your secrets, and mutual secret-keeping reinforces alliances [1]. Journalists, on the other hand, are the gossip queens of the information trade, as they reap their rewards by telling secrets to everyone without much regard for when it's convenient. They are useful only as long as their access can be controlled.
The entry points NSA/CIA used are being watched by them, or maybe even honeypotted. The space of potential attacks is enormous and it's a waste of resources for the Germans to look for them (if that's even legal) as long as America remains an ally.
Please don't take what I am making as moral judgement of one way or another here, just as the practical analysis of the system I imagine these organizations to operate in.
1. Similar to high school cliques or criminals where mutual blackmail creates alliances where there is no access access to the normal judicial system, contracts, etc.
There have been lawsuits against CIA operations in EU before: http://www.nytimes.com/2009/11/05/world/europe/05italy.html?...