If by gypsy trucking you mean point-to-point hauling within the U.S., then I am aware of no treaty that allows Mexicans to perfom this task. A Mexican wishing to haul intra-U.S. would have to comply with any visa requirements, or work as an illegal.
We all know that's a problem, but to blame it on some unnamed treaty is going too far.
Actually, both NAFTA II and the Carribean Basin Initiative were both gutted by Congress (the latter due to business interests dealing with China bribing/lobbying the House), but the Mexicans are still coming. There's a third wave of treaties headed down the pike which will probably be dragged into the sunlight after the elections. The Commerce Department is concentrating on developing India and China right now.
VERY interesting things going on in the Indian IT industry right now, by the way...