When is encryption “criminal”?

Skype automatically encrypts every phone call with AES encryption. Being such, the US government is going nuts because Skype isn’t based in the US and thereby not subject to the wiretapping laws that the FCC ruled on last year.
Amusingly enough, AES is also used by US government organizations to encrypt sensitive data. Since the EU’s Data Retention Directive doesn’t include real-time logging, that still goes against what the US government would want to do.
So it falls into a gray area of how to look at encryption. A lot of corporations use encryption to protect trade secrets as well as communication. When is encrypting a criminal activity and when is it national security?
Via ArsTechnica