That's the best question I've seen in a long time, and one constantly being discussed with law enforcement people, not only on the national level, but municipal level as well. I suspect the RCMP have some more powerful tools than do American cops.
There is no simple answer, there will always have to be some form of interdiction. But, for now, it's a matter of intelligence. We are in a war with the Hell's Angels who are the largest manufacturer of crystal meth in north america. As we knock one down, another pops up, the usual stuff.
And no, there will be no wall, either along the 49th nor the Canada Alaska border. Even if there were the funds, the engineering isn't there. You'd have to build roads in that would cost, unpaved, about $15 million a mile.
In short there are no solid answers. What we must do though, is accept that the current system is not working and start working together, stop arguing from ideological stands, but seek practical solutions. There are a number of VPD, many senior, that agree with me that attacking the problem from the user standpoint is more effective than the constant revolving door of enforcement alone.
Years ago we studied but did a very poor job of implementing the 'four pillars approach, harm reduction, treatment, prevention and enforcement. As airy fairy impossible as it seems, it is effective, even when implemented poorly.
However, like Vietnam, I doubt we will win the war on drugs with land battles. There are simply too many resources and the lure of extreme wealth against us.