They are not. For example, according to Italian Constitution [1], chat control is unconstitutional:

    Art. 15
    Freedom and confidentiality of correspondence and of every other form of
    communication is inviolable.
    Limitations may only be imposed by judicial decision stating the reasons and
    in accordance with the guarantees provided by the law.

note the "EVERY" other form of communication. (Maybe somebody will be able to twist in a way that makes chat control constitutional, or somebody else will argue that since it is an EU law the constitution doesn't matter, but the spirit is clear)

[1] https://www.senato.it/documenti/repository/istituzione/costi...