"For behold, Laban hath the record of the Jews and also a genealogy of my forefathers, and they are engraven upon plates of brass."
The Lord informs Lehi about the brass plates, basically a book, that hold both historical records, such as genealogy, and spiritual records from prophets like Isaiah, and others. Laban, being a high member of the people held the records and had ownership of them. It would be like going to a judge of a court and asking for recent trails and all of the details of them. It's a daunting prospect, even impossible in some cases.
Lord Himself Lehi inform about what? brass plate same book, has thing history and spirit. From prophets same #Isaiah, progress. Laban high person, had plates own them. Same ask judge himself for-for? trial detail have can? think scary, sometime forbidden.