I'm somewhere between the black helicopters crowd, and the all-is-well crowd.
A small example.
In the US, we made a sovereign decision to ban dolphin bycatch in our tuna fleet. And, IIRC, only dolphin-friendly tuna can be sold here.
The Mexican government is in an uproar over this.
http://www.tomzap.com/tuna1.html
Imagine if Mexico were to prevail in the WTO. The US would have to comply, or withdraw from the treaty. I have serious doubts, with globalism and the marketplace being the new religion, that the US would withdraw. And I am enough of a nationalist to be concerned about these kinds of influences on sovereign decisions.
Another example.
Under current treaties, sooner or later, Mexican trucks will be operating in the US. Many of these trucks will not meet US safety standards. Yet they must be allowed, under current treaty, to operate, or it will be considered restraint of trade.
http://www.amo-union.org/Newspaper/Morgue/...News/border.htm
And with Mexico being a major entry point into the US for the drug trade, how much easier will this make it for the drug lords?
Not to mention security in the post 911 era. US Customs already cannot properly search the trucks, ships, planes and railcars laden with imports. This will just overtax them further.
One last example.
Mexican produce on US grocery shelves, and in school lunches.
http://www.sustainable-city.org/articles/mexican.htm
http://www.american.edu/TED/strwberr.htm
My overarching point is, foreign economic interests will frequently collide with US law. And while treaties and agreements must be given due consideration, US law and interests must eventually trump such concerns.