The U.S. House yesterday voted unanimously to ban the importation of trash from Canada, despite protestations from the president that this would hurt U.S. business. At least, that's basically what the first paragraph of the Detroit Free Press article linked above says.
What it doesn't say, however, is the effect of NAFTA on the proposed bill. You see, under NAFTA, the importation of products derived from the NAFTA nations are subject to national treatment, or the same treatment as that offered to nations with Most Favored Nation status. Since there is no ban on intrastate or interstate transportation of garbage, the bill would run afoul of NAFTA, and would probably be improper.
There's a lot more to that, but I'm busy drafting a bunch of stuff for class. This is probably not interesting to anyone but a NAFTA lawyer or someone trying to buy the garbage, but it's interesting to see international agreements (treaties) in play against domestic law.