I don't know that CCA has ever set about creating a formal set of rules for the auctions, at least not one that I've ever seen, and I can't find them poking around the website. (Maybe they're buried in "Meeting Minutes" somewhere, but... heck, the link for the club bylaws is broken.
)
For live animals and plants, they must be properly bagged to be accepted, and any organism that is illegal to sell is ... well, illegal to sell. Duh.
For dry goods, it has to be fish or aquarium related and in sellable condition. Items such as opened containers of fish food, chemicals, used light bulbs, most used cleaning supplies, wet/dirty substrate, broken or leaking aquariums (generally), and anything Reed has ever touched would all be off limits.