Foreign trade is closer to barter than within-national economy. Int econ distinguishes between the balance of trade, which involves the moving of physical goods, and the current account, which includes the balance of trade but also purely financial transactions like investments and remits. International trade proper is seen as unambiguously good, based on comparative advantage theory; international finance is a very different ballgame, and it makes sense that Distrikts would try to control it. For example, the Assembly does this:
If you have international trade but not international finance, you have a sort of barter, but, like Matt says, networked rather than bilateral. To get what this would look like, go back to comparative advantage. For example, the Assembly, for historical reasons, has accumulated an advantage in autonomous small-batch production, so it is a “specialized supplier” distrikt:
The Covenant is strong in very high quality products made by the monks and things that require long-term investment and thinking to achieve; and in knockoffs made by the opportunistic capitalist companies “clustered around the monasteries”.