None of this could happen with a protocol. You cannot require age 
  verification on IRC, XMPP, ActivityPub, Nostr, or Matrix, because there is no 
  single entity to compel. Each server operator makes their own decisions. A 
  government would need to individually pressure thousands of independent 
  operators across dozens of jurisdictions, which is a legislative and 
  enforcement impossibility. And even if one server complied, users would 
  simply move to another.
  

This is wishful thinking. A government would just move to the next layer of the stack and attack the supporting infrastructure, like DNS, payment services or datacenters. To the degree that a protocol is a manner of communication between things (fka services), those things can be made to comply with the prevailing legal authority.