Economist Don Boudreaux puts the burden on those who oppose free trade to explain why trade restrictions between nations will make people better off, given that free trade is the general rule within nations:
Karol, Thomas, and I live in Burke, Virginia. We are free to trade not only with cabbage growers in Culpeper, Virginia, but with cabbage growers in California. We trade freely with residents of any state, from the Atlantic to the Pacific, from the U.S. border with Canada to the U.S. border with Mexico. That is, whatever taxes and burdens Uncle Sam might impose (however wisely or foolishly) on economic activity within the U.S., those burdens are nation-wide. No special space-specific burdens are placed on my and my family's ability to trade with other Americans; no extra tariff or restriction applies to our exchanges with an Alaskan or with a Floridian simply because we do not live in those states.
Practically speaking, therefore, there is free trade throughout the United States. My family and I routinely buy wine from California and Oregon, oranges and lemons from Florida, computer software from Washington state, maple syrup from Vermont, peaches from South Carolina, television newscasts from New York and Atlanta, lumber from Alabama, spicy sauces from Louisiana, crabs from Maryland. The list is long.
And yet no one, not even Lou Dobbs, insists that the Boudreaux family would be richer if only the government in Richmond could fine a successful way around the U.S. Constitution and managed to slap stiff tariffs on California wine, Florida citrus fruits, cajun seasoning from Louisiana, and you name it.
...
Anyone skeptical of free trade must explain why political borders are economically relevant. With the exception of pointing to (mostly rather vague and poorly considered) national-defense issues, protectionists have never managed -- and I dare say never will manage -- to impart genuine economic relevance to political borders.
