In short: By the time a person is 18, they must effectively be able to communicate and understand conversationally in 2 languages and casually use them in daily life..., if not become completely fluent...
Other than that, any language goes (whether it is a locally-known one, or a popular one worldwide),
The only thing I hope to gain from this, is to rid the world of /Monolingual Betas/
Seriously though, has this been a policy before? Because I haven't heard of such one...
I think this can especially be used for citizenship...
Edit: I don't necessarily have any other presupposed requirements besides bilingualism, though we may have certain notions of such in this main goal
Edit II: In furthering this venture, I have realized that my liberalism may slightly poisoned my lens....
And for clarification...
Minimum dual language system:
Main national language + other language (likely another related language, but foreign ones are fine)
So if someone doesn't know two languages by the time they turn 18 they would get their citizenship taken away? Anyway what I was getting at is that citizenship is basically a person's personhood under the current state system, so there should really be as few things tied to that as possible (birthright and/or residency only imo)
I prbly should've stopped myself from typing that...