| The civs you gave your trade good to never lose the advantage of it. Even if they are at war with you. |
Yeah this is a real shame and something to bring up for later patches I fee... I mean, I can see why it is this way - so you dont exploit them by selling all your trade goods for tech to the AI then immediately declaring war on them!.
Instead, you should be able to sell them a trade good for a limited period only, say yearly or whatever.
I dislike the idea of selling any of my permanent bonus trade goods to an AI that can turn round and stab me in the back later. With a time limit, you could at least refuse to trade it the next time if the AI has been warring with you.