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 should apply equally to all.

First of all, it's a permissive blockchain similar to e.g. Ripple and Stellar, both of which are used by companies in the EU; some of which are fintech companies actively collaborating with the German, French and other governments. Some of the coins on these platforms are stable coins for euros, dollars and other coins. Some of them represent bonds (e.g. a German company called Bitbond) and some of them of them are new coins. Some EU companies even offer credit cards backed by crypto currencies (e.g. Wirex is based in the UK and offers it's products to people in Germany and elsewhere).

Then there is the notion that quite a lot of EU citizens own and actively trade in bitcoin, eth, and a wide variety of other coins already. Why would a Libra coin be any different just because Facebook is behind it? The scope of what they can ban here under existing laws seems unclear. Making new laws takes ages and has so far not really happened. Most blockchain companies operate under interpretations of the existing laws. My guess is that market making for Libra like Facebook is planning would probably be subject to regulation and also be problematic in many other countries (like the US).

Then there is Move, the language used for implementing smart contracts in Libra. That too already exists in the EU market in the form of loads of companies doing all sorts of things on top of mainly Ethereum and using Solidity, which is technically similar. You can argue about how useful these things are but there is a lot of investment happening in startups doing things with block chains and smart contract. A lot of that is happening with permission of the relevant authorities. E.g Bitbond was approved by the German Bafin.

So, singling out Facebook to do any of those things does not sound like it would be very practical from a legal point of view.

What they can do is take action if Facebook starts promoting and trading it's own currency within Facebook which I'm guessing would require a bank license or at least expose them to financial regulation.

My guess is that Facebook will instead launch Libra with a simple stable coin backed by euros and dollars and post pone launching their own coin. This would make it more similar to what e.g. Apple Pay and Android Pay enable: a simple online wallet that users may use for paying for things online. The fact that there's a blockchain involved is maybe technically interesting but not necessarily a problem. I'm guessing they'll also be exploring using smart contracts for a few things. Facebook as a payment provider would of course be subject to the same kind of rules that Apple, Google, and others have to deal with.

A further complication might be that Facebook is isolating Libra into a separate foundation. That might shield them legally and allow them to push some boundaries. One thing they might eventually do is launch Libra the coin only in certain markets. They were talking a lot about third world countries in the original announcement.