For anyone who may not know, there are ZERO laws saying that the price on the tag is what you HAVE to sell it for. I've had this line used on me before and later checked my state and national law. Found zero evidence supporting this "law."
Yes while it is nice for customers to shop at your store and get x desired item for a great price, the retailer does NOT have to sell an item ringing up for $1.50 when you know it's $20, even more so if the item you're scanning is a shirt and it's ringing up with a description of a notebook.
If such a law existed then it'd change the retail game altogether and tag changers and sticker peelers would win while companies lost money. Only time I agree with selling an item not on sale for cheaper than it should be is if there's a lot of that item under a sign or the like. Otherwise if the description doesn't match or I know it's a new item I tell them it's not that special sale price, that it was put in the wrong place or mismarked.
So next time someone wants to throw this "law" in your face just hold strong!