It's called the Shop Like a Local rule, from 2018.
Basically, Apple can stop selling developer accounts in Italy if they wish. They might run into issues on discrimination grounds, but it would probably be a long fight.
However, they can't prevent an Italian developer from purchasing a developer account from another EU country.
https://eur-lex.europa.eu/EN/legal-content/summary/geo-block...
I don't understand EU law, but wouldn't the country where the purchase happened be the one whose laws govern the transaction? In other words, if an Italian purchases a developer account from Germany, wouldn't any disputes be handled in German court?
(Also, I would assume Apple would require a developer to have a legitimate physical business address in a country where they allow developers. I don't imagine this would be an easy transaction.)
The opposite -- Italian law governs because the developer is Italian, even if the developer makes the purchase in Germany -- seems untenable even by European standards.