The immediate problem with legal system is not even persuation, it's the burden of untangling the facts.

Experts who should be using their knowledge are tempted to use AI to make their arguments to save time and effort. AI will happily comply even if it has to make up laws and precedents, and most individuals and small businesses would not have the savvy and resources to figure it out. Even if they do, it ends up as a challenge in court, which acts a straightforward amplification attack against an already overburdened legal system.