In arguably biggest test of new NAFTA, Canada and Mexico defeat U.S. in auto rules dispute Dispute over content requirements seen as a litmus test of new trade pact Canada, Mexico and auto companies have been declared the winners in arguably the most important trade dispute under the new NAFTA, landing the U.S. on the losing side in a case about calculating the origin of auto parts.The long-expected decision was known for weeks to the parties involved, yet it was withheld from public release until after North American leaders appeared together at a summit this week in Mexico.Canada, Mexico and the auto industry are now celebrating the ruling from a five-member international panel.Early reaction was vague from the Office of the U.S. Trade Representative (USTR): It did not spell out its next move, but called the decision disappointing.Canada: U.S. was trying to sneak in changes Canada's submission includes correspondence as evidence that the parties were stunned when the U.S. presented this new formula in 2020, after the pact had already taken effect."