I don't think so, all that is needed, is control of the border... Most pot comes from the good 'ole USA, pot is the biggest U.S. cash crop as it is the most commonly used drug in the U.S. and that has stayed fairly steady for a very long time.
Are you sure most pot used here comes from the US? Our government isn't so sure about that. Most estimates are that more than half comes from Mexico. They believe that in 2007 15,500 metric tons were produced in Mexico and most of it came here, and more was produced there in 2008, again with most of it coming here. There are parts of this country were mostly what you will find is domestic grown, but Mexican can be found most everywhere and throughout much of this country it completely dominates the market. They believe the total amount available on the market here in a year, foreign and domestic, is between 12,000 to 25,000 metric tons, and that Mexican pot could make up well over half of what is consumed here.