It is possible to do, to some extent. Everything’s possible. But then, when people that are on both side of this encryption barrier wants to talk, then both must use unencrypted messages. You’d also have the obvious case of someone having a phone/device/account from country A temporarily crossing through country FuckingFranceOrUK, so what do you do in that case?

You’d need to implement that, add UI features to know if you’re using encryption or not, and above all, it’s fucking stupid and against what most sane messaging solutions wants to do.

I’m sure it’s possible to find people that would gladly do all that. Hopefully those people are not in the business of making all the useful communication services we currently use.