The only wording I might think would be needed is "Anything that another player could not use because of a soul bond or other similar type of enchant is not permitted to be sold on the market." I would have to agree that "end-game" items should be barred from being on the market.
If that vernacular is already in the rules then my question now becomes why is this even an issue. Follow the rules period. If you can not follow the rules then get a warning. After you have been warned twice and your item deleted then be subjected to a nuisance temporary 1 day ban. Add 1 day for every infraction thereafter.