On: GDPR for lazy people: Block all European users wit...

[amarkov]

I'm not aware of any rule or case which supports this claim.

[viraptor → amarkov]

It doesn't have to be a specific rule. You learn that the age declaration was invalid so the "§312.10 Data retention and deletion requirements" applies unless you have a verifiable parent consent.

[seanmcdirmid → viraptor]

Not many companies are going out of their way to learn that their users are lying about their age.