The prohibition on narcotics predated the 18th Amendment (Harrison Act of 1914). To answer your question simply, the Constitution is dead (as both Dr. Woods and Dr. Gutzman have written about in their book on the topic), and the political class in D.C. has not cared about constitutional restraint because the people that put them in power have not held their feet to the fire, the States have been emasculated (charges of racism), and the State representatives have been afraid to push the issue..
