Go to where the Card Queen is (if you haven't started her quest she should be in Balamb by the train station), and challenge her to a card game. When you get to the rules screen, check the the trading rule. If it's still Direct, cancel and repeat.

If it's anything other than Direct (One, Diff or All), cancel and go challenge the closest other person. Make sure the new trading rule stuck, and if it didn't, repeat from the start. If it did stick, save your game and go back to the pub owner. Challenge him and make sure the trading rule carried over to this region as well, and beat him. Direct is the only trading rule that restricts the cards you can win to the ones you turn over, so you don't need to turn over the Doomtrain card to win it anymore.