Yes, I believe it is not legal. That’s what I told him…yeah they legally cannot do that. I believe something similar happened at Cartier if I am remembering the brand correctly (web error caused an item's price to be significantly lowered) and they canceled the customers order and that went to court. Ultimately settled out of court and the client "won"
I am appalled that this situation has become a reality for you. I'll let others chime in on their thoughts and how it may ultimately impact your relationship with the maison.
I asked to speak to the manager.