First of all, it is often a question of personal initiative. A person who really wants to access this position will try to learn French. The person may become even more interested in civil law, while they're at it. We talk a lot about bilingualism, but we could also talk about bijuralism. Let’s just stick to bilingualism for the time being.
This must come from within first of all. Law schools may also make French courses accessible to students. However, it is not possible to isolate a pool of potential candidates if they don't make their ambition public. I think it will basically be personal initiatives, but I hope they will be supported by the law schools.