Can someone familiar with Libra speculate how a ban can be implemented? What comes to my mind is forbidding Facebook selling and processing it for EU users but beyond that, I am not sure how a "black market" could be prevented.
I'm not sure France and Germany fully get what they are trying to ban exactly. Most politicians only have a very rudimentary understanding of this stuff and probably lots of misconceptions. Libra is several things; most of which already exist in other forms in the EU. That makes it hard to block as a whole. At least not without also impacting a lot of other companies and people doing similar things because the law sh…
Other blockchains have not been blocked outright because they don't pose a threat and are developing slowly, so EU countries are working towards more or less sensible regulations. Facebook has far more power to drive adoption, so in order to avoid a situation where Facebook screws up (intentionally or unintentionally) they block the currency preemptively.
> quite a lot of EU citizens own and actively trade in bitcoin, eth, and a wide variety of other coins already
Relatively, not that many. Also, those currencies are being mostly used as investments, not currency.
> Why would a Libra coin be any different just because Facebook is behind it?
Precisely because Facebook is behind it: a foreign company, known to bypass and ignore regulations, with interests that do not necessarily align with those of the citizens, and with zero accountability.
> startups doing things with block chains and smart contract.
As long as it is not a global currency owned by private corporations it's ok.
> This would make it more similar to what e.g. Apple Pay and Android Pay enable
A different coin is very different from Apple and Android Pay. Payment systems are very different from coins.