Answer: Apart from the inevitable anger on the part of the U.S. government there would be very little, if any, immediate consequence of significance. There are two possible scenarios.
Case I: Canada would immediately offer to negotiate a Fair Trade Agreement with the U.S. and Mexico which would maintain the status quo on tariffs, dispute settlement mechanisms, etc. but which would not include the unacceptable “national treatment” clause on investment, the energy sharing provisions, etc.
If the U.S. and Mexico agreed, trade would not be affected but Canada would have regained the right to reinstate the Foreign Investment Review Agency which would be able to screen foreign investment and apply conditions as well as limits on the level of foreign ownership acceptable in any industrial or resource sector. We would encourage foreign investment but only when it would be of benefit to Canada. Jobs would not be lost and might even be enhanced if we stop selling companies that are subsequently downsized or shut down completely. In sum we would regain control of our own destiny. (Existing investment is not affected.)
Case II: In the event that the U.S. and Mexico refused to sign Fair Trade Agreements, Canada would revert to reliance on the General Agreement on Trade and Tariffs (GATT) which served us so well before the FTA was signed.
We would then rely on the WTO dispute settlement mechanism.
Our tariff advantage with the U.S. prior to 1988 would be re-instated.
We would achieve the same investment advantage that we are seeking vis-à-vis the U.S.
The only negative – which might turn out to be a positive for Canada in repatriating some of its talent – would be that the TN Visas under NAFTA would not be renewed when they expire.
N.B. Under both scenarios Canada should ensure that it doesn't give away more sovereignty under the WTO General Agreement on Trade in Services (GATS) which the Liberal government is in the process of doing.

"The greatest price of not participating in politics is being governed by your inferiors." Plato
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Dave Ruston
"The greatest price of not participating in politics is being governed by your inferiors." Plato
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"We can only see a short distance ahead, but we can see plenty there that needs to be done." - Alan Turing
Dr. Caleb, I didn't expect to be going to the National Post site. Whenever you go there all kinds of ads get stuck to you when you leave.
"The greatest price of not participating in politics is being governed by your inferiors." Plato
For example,Foreign Investors have the right to sue our governments, if they feel that they are not given "national treatment"
The US company, Ethyl corporation, in 1998, tried to sell a gasoline additive, MMT, which was banned in the US, in Canada. Our initial reaction ofcourse was to ban0 this product, MMT, which was proven to be a nerve toxic. The US has the right to sue us (due to the Chapter 11 clause of NAFTA) They claimed that we were not abiding by NAFTA rules and so we settled out of court. We payed them about 13 million dollars. They had initially sued for $250 million. We then, to pour salt on our wounds, lifted the ban.
So not only is our government paying out millions of dollars that could be used for public services, we also put our the health of our children, families and friends at risk. This is all in the name of a better standard of living? Did NAFTA provide the panacea we were looking for or did it just further dig the grave of our sovereignty?
We need to take responsibility for the decisions we make. It was a mistake to sign this agreement and we have a lesson here. We just need to swallow our pride and say it. We are only human and it was a mistake. Its now time to make some changes.
We must as a whole consider this problem. It is true that 85% of our exports go to the US. Most of that is Lumber and Energy. Right now, the US, does not have the resource capacity to sustain their consumption. They do need us. We will have the wind knocked out of us for a bit if we abrogate.. but it would not be like north Korea. It would actually be a democracy. Canada would regain its policy autonomy. We dont have that now..and it will continue to decrease as our domestic companies are bought out.
So think about this.. and know that its up to the people to make changes.. to let our governments know what we want and also what we dont. Canadian History has shown us, that by not speaking up, not caring, we become victims. We still have this chance to change for our future generations. We must act now while its still possible.