Products can only be listed on Amazon if the seller states the condition they’re in. Amazon lists its condition guidelines here. Note that they do not correspond to the guidelines you’d see on eBay, Abe, etc., and they can be different from one category to the next. You may also find a few pointers in this blog post. Amazon is strict when it comes to product conditions, so it’s better to err on the side of caution. An oversight can lead to a suspension.