The only way to 'enforce' auction rules would be through an ingame system (like they do in some other MMORPGs).
You put an item in the 'auction house' with a 'starting bid' and a 'buy now' price. (with 3 monetary values : meseta, PDs and dts)
You select a time period in hours (max a few days)
You submit your auction item and it remains in the system until it's either sold or withdrawn within the first 10 minutes (e.g. you made a mistake with the pricing)
People who want to bid on it, select a certain amount and place the bid. You can't take the money out until someone overbids you.
But as Soly said, auctions are something you need to have your own responsibility in. It's a system where the buyer wants the most value out of an item and thus should cope with a certain level of uncertainty when an offer is too good to be true. If people constantly withdraw their offers or break other rules, they'll pretty much ruin their trading reputation and will have a harder time buying something. Implementing a system like I mentioned above takes quite some work and has to be completely safe/exploit-free. Afaik there were no real item auctions in the forum several years ago.