Excellent article.
https://mises.org/library/clarificat...ase-free-trade
From the article:
Since the time of Ricardo, the key assumption of trade theory remains, in the recent words of trade theorist Roy J. Ruffin, "the inability of factors to move from a country where productivity is low to another where productivity is higher." In a recent article in
History of Political Economy (34:4, 2002, pp. 727-748)
, Ruffin shows that Ricardo’s claim over Robert Torrens as the discoverer of the principle of comparative advantage lies in Ricardo’s realization that comparative advantage, the basis of the case for free trade, lies in "factor immobility between countries." Ruffin notes that "of the 973 words Ricardo devoted to explaining the law of comparative advantage, 485 emphasized the importance of factor immobility."
If factors of production are as mobile as traded goods, the case for free trade--that it benefits all countries--collapses.
There is no known case for free trade if factors of production are as mobile as traded goods.