Youre absolutely right. They also found that alcohol, tobacco and oil cross state lines. And they are the last word. You can however change the constitution if you can rally all the libertarians who never use dope in one mass movement for the good of the children.
Why would we want to do that. It's much easier to coerce the USSC into say it means something different. Thank God for FDR, or what's growing in a flower pot on your window sill, or what's living in a mudpuddle in your back yard wouldn't be a federal matter, and thousands of bureaucrats would be out of a job.