https://www.patrick-breyer.de/en/chat-control-2-0-trilogue-u...
> given the constitutions of various EU countries
EU law superseded any state law by default and that's by design. Even if the EU law is immoral and dangerous like the Chat Control law.
So a country's constitution will not save you if tomorrow all chat apps are doing client side scanning.
In practice it _might_ still save you, if the country is willing to pay annual fines to the EU for not implementing some law or policy. But communication tools are always at least a 2 way thing, where you communicate with someone else. If that someone else has their chats leaked due to living in another EU country, where chat control is implemented, then even your constitution will not protect you.
Scenarios like these make me consider, whether one day I need to vote for my country to also leave the EU, as it might become a surveillance nightmare. The moment chat control impacts me and my chats on my devices, I think I will have had enough of this. But the economic consequences are scary of course. So damned if you leave and damned if you don't. Sucks.