I think what's needed here is for A/I to go the ECHR.

A state failing to prevent foreign sanctions from restricting the freedom of association of its citizens is certainly a breach of article 11. It doesn't matter whether it's caused by a foreign state, the duty of Italy is clearly to ensure freedom of association in practice.

How is Italy going to do that?

You could argue that all the nations that have signed up to the ICC have a duty to protect its officers from American sanctions and that is clearly not happening.