I have often wondered about the legal basis for the prohibition on cannabis. I always assumed it must be the interstate commerce clause but I could never make out why we needed an amendment to outlaw alcohol.
We didn't. We needed an amendment to ban alcohol in a way which could not be undone without a subsequent Amendment; the 18th Amendment banned alcohol itself, it didn't grant Congress discretion to do so.
a bit ironic now when we have a president railing against mexican cartels and promoting prohibition of marijuana.
those who do not learn from history are doomed to repeat it and all that...