How so?
How not so? NAFTA allowed non-market economies to trade with market economies, and paved the way for the deluge of regulations that followed. A free market does not permit beggar-thy-neighbor policies, nor does it make boats sink rather than float with a rising tide. Like I said, it is a false dilemma to posit a Scylla/Charybdis choice between free trade and mercantilism.
Marx would have not have endorsed free trade so enthusiastically if he had not seen how ready of a vehicle for an attack on society it was.