Would be interesting to see a govt tackle setting up a trustless system like it required for cybersecurity best practices. I think it's a thorny issue without a trusted authority though.

What stops an ID for being posted publicly or shared en masse? So one ID can be used unlimited times - just share the key with minors for $1 at no risk to oneself since there's no knowledge of the 'transaction' being sent around. Better for individual privacy but that undermines the political impetus for wanting the verification. Usage would probably have to be monitored or capped, kind of defeating the advantage of the anonymous protocol (or accept that abuse is unenforceable).

So how would you use it to solve this problem? There still needs to be some sort of foolproof way of saying “person X is only 14 years old”.