Illicit drugs are illegal for thee and me.
For just a second, set aside the drug issue. What would Thomas Jefferson say about our society and our government if he were alive today? Don't you think that the society/government to which he was referring doesn't exist today?
The world isn't flat, so to take quotes from the Flat Earth Society would be pointless. Ditto Jefferson.
If our society and our government today were as Jefferson described, I would understand your argument. But I'll have to go with Ann Coulter (ex-Libertarian) on this issue and work to change our society to be more like Jefferson's ideals before addressing the drug issue.