NAFTA allows prison-made Chinese textiles into US via Mexico

NAFTA establishes rules that deny preferential treatment for goods produced outside of North America. The way for a Japanese or European company to get preferential treatment, of course, is to build a factory in Mexico. US textile makers who want to be competitive will be forced to move jobs to Mexico or go out of business.

Assume the US could put enough customs agents along the border to inspect every item exported from Mexico to the US. Are those customs agents going to be able to tell the difference between a shirt made by prison labor in China and a shirt made in Mexico