There's a whole thread on this forum somewhere about them and other people getting letters, etc. Several threads on the Amazon seller forum too.
EDIT: Adding link to thread:
Has anyone here had issues selling Lego through Amazon? I just got a letter from a law firm saying it’s unlawful since I am not an authorized seller. It’s the same letter that was posted here a few years ago from VORYS. Do you guys know what ended up happening?