Well hang on, "just work" implies an objective standard of correct vs incorrect. No such standard exists. I'm sure that there will be legal AIs that reliably do... something... but the whole point of the legal system is to allow space for humans to argue their case. If an AI "does legal" deterministically, without human intervention, how can it be said to be "working" if its very use defeats the purpose of the system it has learned to navigate so expertly?