Users younger than 13 are deleted immediately once SE is informed about the case. The reason for this is COPPA, the US law intended to protect children online.
The guidelines as far as I understand them for me as a moderator are that I should report such users to SE, and they'll use a special deletion procedure to comply with the law.
The recent post on MSOrecent post on MSO about this topic made me wonder, am I actually required to report such cases to SE? I don't think this specific law serves any useful purpose in the case of SE, and I'm not a US citizen anyway. From that point of view I don't see any reason why I should help to enforce this.
But I am also a moderator, so I'm bound by a few more rules, the main one being the moderator agreement we all have to agree to. I'm acting on behalf of SE to some extent, but not really in a legal way as far as I understand.
Do I as a moderator have an obligation to enforce the minimum age here on SE, do I have to report any user below that age that I notice, or am I free to ignore such cases?