I think it might have been in 1997, or shortly after the Kyoto Protocol was adopted, but it would be difficult in 2006.
That said, I think the federal government could certainly implement a hybrid system, so that the provinces that want to could address this on a territorial basis. Certainly, a province like Quebec would be interested—there may also be others—in this kind of system.
If a cap on territorial emissions were put in place, I'm not sure that would go over very well in Alberta, politically. During the ten years that we wasted, we didn't even consider this. It might have been difficult, even in 1997 or 1998, but we didn't even go through the exercise. I guess we will never know. For some provinces, it is certainly a possibility. Some have made it abundantly clear that this is how they intend to proceed.