I slapped together a little something (g) for Germany's Legal Times Online about the Snowden case. The editor pepped up the language a bit, but that's fine with me, it's supposed to be a popular format.
What I said is that the Fourth Amendment guarantees US citizens privacy in situations in which they have a 'reasonable expectation of privacy'. Email and (especially) phone calls certainly belong in that sphere. So if the NSA is collecting massive amounts of emails and telephone data randomly, without a specific search warrant, then it is violating the privacy rights of US citizens. According to recent revelations, the NSA has developed internal 'minimization procedures' that instruct agents to stop listening or reading if they find out that they are spying on a US citizen, similar to regulations the German Federal Constitutional Court has required in cases of spying on telephone calls or private apartments. But since the court meets in secret, we have no way of independently verifying these claims. Also, since the Obama administration has blocked all privacy lawsuits with the legal doctrine of the state secrets privilege, no American court has yet ruled on whether these programs are constitutional.
However, the situation in Germany is not very different. German spy agencies have extremely broad powers under existing law, and will gain new ones under the new Telecommunications Law which takes effect on 1 July. There is a parliamentary committee which provides general oversight of requests for surveillance and a so-called G-10 committee which rules on individual requests. They are supposed to follow strict minimization procedures and insist on adequate proof of possible wrongdoing before authorizing spying measures. However, since both of these committees operate in secret, we have no way of knowing how carefully these guidelines are respected. Plus, since there have been no German whistleblowers, we have no real insight into the scope of German programs. As the Green Party speaker Konstantin von Notz recently remarked, it is high time that Germans learned more about what their own spy agency is up to.
One thing that has really angered Germans is the fact that communication to and from and even within Germany are being spied on by the US and the UK. The official position of the US government (in the form of a Senate report) is that foreigners 'foreigners outside the United States generally are not entitled to the protections of the Fourth Amendment.' Thus, the current version of Section 702 of the Foreign Intelligence Surveillance Act provides no protection for the privacy rights of foreigners. The secret court which orders surveillance can authorize blanket data collection on all foreigners, everywhere. The only limitations kick in when it appears that an American citizen may be involved. In the words of the report itself, 'Section 702 thus enables the Government to collect information effectively and efficiently about foreign targets overseas and in a manner that protects the privacy and civil liberties of Americans'.
Of course, this wouldn't matter so much if American and the UK didn't have, and use, spying technology that can sweep up massive streams of data from everywhere and anywhere. As far as remedies for Germany, it's not clear what Germany can do, except send sternly-worded letters (g) to American officials. I'm not aware of any treaty that the US has ratified without reservation which would give Germany a basis for complaint before international tribunals. But I'm happy to be corrected in comments if I've overlooked something.