I dont see how is going to work, only how is set. Maybe I miss it.
But as before, this will mess with the market economy. Huge Alliance will Embargo every trader except the ones they want to support, people will use the mechanic that way. And people will create Alts to try to evade it.
Is not moral, but is logical to sell what you build. It happens in RL, countries selling their weapons to other countries which are at war with Allied countries…