Now that the U.S. has changed course on the TPP and the other signatories, including Canada and Mexico, are planning to ask China to join, ruthless capitalists, both American and foreign, are no doubt planning to take advantage of the loopholes in NAFTA.
Just to take one example -- Annex 401 - Specific Rules of Origin, Chapter 85: Electrical Machinery and Equipment and Parts Thereof; Sound Recorders and Reproducers, Television Image and Sound Recorders and Reproducers, and Parts and Accessories of Such Articles -- assemblies will be considered to be valid Canadian or Mexican NAFTA imports if their domestic content is "60 percent where the transaction value method is used, or 50 percent where the net cost method is used."
The 60/50 rule is in effect for every manufactured assembly, including, but not limited to: electrical and electronic equipment, and parts thereof; nuclear reactors, boilers, machinery, mechanical appliances, and parts thereof; vehicles, aircraft, vessels, railway / tramway locomotives, and parts thereof; optical, photographic, cinematographic, measuring, checking, and precision equipment, medical / surgical instruments and apparatus, clocks, watches, musical instruments, and parts thereof; and furniture, bedding, mattresses, mattress supports, cushions and similar stuffed furnishings, lamps and lighting fittings, illuminated signs, and prefabricated buildings.
The confusion begins in Chapter Four: Rules of Origin, Article 401: Originating Goods where "a good shall originate in the territory of a Party where ... the good was imported into the territory of a Party in an unassembled or a disassembled form but was classified as an assembled good pursuant to General Rule of Interpretation of the Harmonized System."
The arcane regulations are beyond me, especially the important detail of what percentage of the overall product is assigned to the assembly of subassemblies which were manufactured in another country. It does seem that it would not be a violation of NAFTA for a capitalist to open a factory in Canada or Mexico and assemble complex electronic products using printed circuit boards and other parts manufactured in China, violating the spirit, but not the letter of NAFTA law.