… is from page 306 of James Doti’s and Dwight Lee’s Introduction to Section 8 (“International Trade”) of their excellent 1991 collection, The Market Economy: A Reader:
The benefits of free trade are readily acknowledged for trade that occurs within a nation. Indeed, the success of the U.S. Constitution as compared to the earlier Articles of Confederation was in large part due to the Constitution’s adherence to free trade principles that broke down government-imposed trade barriers between states. Yet, while free trade among exchanging parties within a nation is a right generally protected by a nation’s laws, free trade among nations rarely exists.
The divergence in policy regarding inter and intra nation trade policies seems even more puzzling in light of the great abundance of economic analysis from [David] Ricardo to the present that in the main shows clear and significant gains from free trade among nations.
DBx: What Jim and Dwight say. (I add only that the abundance of economic analyses showing the productive powers of free trade began to accumulate even before Ricardo (1772-1823) wrote. Adam Smith (1723-1790) famously, brilliantly synthesized and firmed-up much of this analysis in 1776 – but even Smith was not the first on this front.)