I'm looking into buying AC Milan tickets in April while we're there for vacation. Apparently in order to get access to lower sections, you need to be a "member" (Cuore Rossonero), which costs 20 euros for four years. Even looking at third party sites, they say you need to bring ID + the card in order to go in.
I'm not naive enough to think MSG would ever implement this (we need as many bodies as we can get...). But it's an interesting strategy to make sure your home crowd is your home crowd. Just figured I'd share for some international perspective.