If you wanted to truck oranges from Miami to New Orleans, it doesn't matter where the truck was made. If you wanted to fly them, it doesn't matter where the plane was made. But if you put them on a boat, the Jones Act says the ship must be American made or be subject to tariffs and fees. How much of a difference does this make?
Enough so that the administration temporarily waived the act so as to get shipments to Puerto Rico after hurricane Maria. Evidently, they believed this measure was restricting the free flow of emergency provisions. But, alas, the waiver will not be renewed. Some clever economist should measure how much this waiver lowered costs (and maybe saved lives). If so, we might have the ammunition needed to repeal this blatant protectionism.