However, come next election, should the left unite, the story could change drastically. In that case, should free trade become politically unfeasable for the government, waht kind of protectionism would you be looking for?
As for myself, one proposal I could see would be raising the cost of resoruces such as gas. It is somewhat protectionist in that it makes local products more attractive than products from farther afield owing to the cost of transportation. It is not totally protectionist though in that, for example, while an Ottawan would find a product from Gatineau or Toronto more attractive price-wise than a similar product from New York State, he'd still find the product from New York State to be more attractive than an equal product from British Columbia. So though it's still not totally protectionist, it still is to a degree.
Another element of a gas tax or other resource tax is that it is not just protectionist but also fair in that just as an Ottawan would find a product from Mexico less attractive than a more local product owing to transport costs, the same would be true in reverse (the Mexican would find Canadian products too expensive for the same reason). So while a high gas tax would reduce Canadian imports, it would also reduce Canadian exports. So while foreign companies might become more tempted to move to Canada or at least to the US near the Canadian border to serve the Canadian market, Canadian companies might also be willing to either establish branches abroad or at least in Southern Canada near the US border so as to avoid the cost of gas to export its products. This would mean taht while Canada would be protecting Canadian jobs, it would not be engaging in immoral beggar-thy-neighbour protectionism but rather engaging in fair trade that can also allow Mexicans to develop their economy too on an equal footing with Canada.
Also, unlike tarifs and quotas, a gas tax would not create artificial inefficiencies involving artificial geographical delineations by requiring eastern Canadians to have to buy from BC when they could just buy from New York state for example.
As for the issue of some companies possibly simply establishing themselve on the Canada-US border, a simple solution would be to establish a free labour movement agreement whereby crossborder workers would be taxed based on country of residence and not country of work, but would also be free to seek work across the border.
I think such a fair-trade agreement would still protect Canadian jobs at least in the Canadian interior without necessarily engaging in the beggar-thy-neighbour economics that would necessitate economic retaliation or that woudl hurt developing countries.
Again, I'm more for truly free trade, but should that ever become truly unfeasable, then a simple gas tax woudl likely be a better compromise than outright tarifs and quotas.