MAP Pricing

Hey, We have been currently selling a certain brand of product which we purchase through distribution and not direct. However we literally took several pallets of stock and listed the lines with Amazon’s reprice tool. We then took a call from the brand owner stating our selling cost is below their MAP pricing (bare in mind we was not aware of the MAP pricing) as we bought this through a distributor and not direct. I then looked at the listing in question and raised a point stating you have 2 other seller’s on Amazon who are selling cheaper considerably. To which the brand owner has stated that the 2 other sellers are allowed to sell 10% cheaper than MAP pricing however every one else has to stick to MAP pricing. Is this legal? to me there seems to be some sort of competition law but I do not know in great detail. The company has also given brand registry to one of the sellers so they have the ability to remove us from the listing if we do not comply. Any thoughts?