If the seller of a kellog's mileage certificate and the buyer of a mileage certificate do not have Advantage accounts, how can they be breaking any rules. If you do not have an account, you have not accepted any of American Airlines terms and conditions. (even if you do have an account, you are not buying/selling/bartering miles from that account). How can American threaten anyone if they have not agreeded to any of the terms? There is no state or federal law that prohibits this and American can't close down an account that does not exist.

If American was concerned about this, they should have put a disclaimer on the coupon that they could not be bought/sold/or bartered and they did no such thing.

Last but not least how is this hurting anyone? Kellogs got the money from selling the product, American got money from selling the miles to Kellogs, the buyer and seller are in agreement on the price and the seats given away for the miles are capacity controlled.