What may look to one observer like the application of objective standards may appear to another observer as improper protectionism. Originally signed in the mid-1990s, NAFTA calls for an open border for commercial truck traffic among Canada, the United States, and Mexico. But in early 2005, Mexican trucks were still not allowed into the United States, due in part to litigation brought by environmental and labor groups. Their claim was that the United States hadn’t appropriately considered the environmental impact of letting Mexican trucks roll on American roads because there are no standardized emissions rules for commercial vehicles. On balance, does this argument sound to you more like a principled objection or like protection for U.S. jobs? Why?