Resellers fraudulently claiming a liquidated item is new, or that they are an authorized distributor allowing for the product to be warranted, is its own problem. It's usually not a large enough fraud that it's worth it for law-enforcement to follow up on, but generally online marketplaces, like eBay, have their own enforcement practices to keep traffic away from fraudulent sellers.

On the author hand, Amazon has made it difficult to avoid fraudulent sellers, but they also don'e even sort items by price when that option is selected, so I avoid buying through their site.