What's even more interesting is that, as far as I can tell, Mexico is under different obligations than Canada (see the G&M article I link to above, where the next pgh after the one I pasted above reads):  "Proportionality favoured the short-term interests of exporting corporations and producing provinces, to the detriment of using Canada's raw resources to make other things, and for long-term energy security for Canadians.  The Mexicans were smart and got an exemption from energy sharing in times of shortage. Look at the respect that exemption got Mexico in the U.S. national energy task force report: 'Mexico will make its own sovereign decisions on the breadth, pace, and extent to which it will expand and reform its electricity and oil and gas capacities.'"

Out of fairness, here's a link with all of the NAFTA "pros": http://www.fas.usda.gov/itp/Policy/NAFTA/nafta.html