

If my gov creates a digital cert of age and signs it then I should be able to use that and the service provider can verify against gov public key, no? No information of visit exchanged.
As an alternative I also expect it to be possible via zero knowledge proof https://en.m.wikipedia.org/wiki/Zero-knowledge_proof
Having trade deals on both sides doesn’t man you can ship whatever from one to the other.
They can trade over set of things with one, and another set with the other.