The Joint Declaration was agreed upon at an informal meeting of the European Chiefs of Police in London hosted by the National Crime Agency on 18 April.
Police Chiefs of all EU Member States and Schengen Associated Countries were invited, alongside Europol’s Executive Director.
Here is the declaration (pdf).
And letters. If you go to the stasi museum in Berlin they have the letter opening equipment as proof of how despicable they were.
The West did (and still does) spy on people to a similar extent, they just have been less obnoxious about it (wholesale spying, but no wholesale persecution) so nobody gets too upset and makes a revolution or something.