The only way to guarantee that is to have a lawyer not armed with LLMs.

We've seen dozens of examples already of lawyers doing exactly that. (Some of them have then doubled down in court, to their eventual detriment.)

If you're making a habit of using LLMs to draft briefs for you, how long before you just forget to check the cited cases to replace the hallucinated ones with real ones? Or decide not to check, because surely they'll be fine this time...only they're not?