Where confidence in the State of Law starts shivering is when new laws/regulations are implemented with retroactive effectiveness, whereby it is immaterial whether it is a new law governing sovereign bonds or any other new law.
I have never heard anyone argue credibly that a civilized society can advance without a well-functioning State of Law. It is not only that laws must exist; there must be a shared belief in society into that State of Law.
Any retroactive effectiveness of a new law severely shatters the belief in the State of Law. Going forward, every potential foreign investor in Greece will have to ponder in depth to what extent he can trust laws which may be changed with retroactive effectiveness.
Personally, I think to “play around” with retroactive effectiveness of a new law is about as good an instrument to scare foreign investors away as any!