This is the second part of a two-part series. Read part one here. Americans spent approximately $100 billion a year on illegal drugs between 2000 and 2010, according to a 2012 report published by the RAND corporation. Part of the Drug Enforcement Administration's job, alongside several other law enforcement agencies, is to make that process more difficult at home, where harsh federal drug laws have ensured that such transactions are conducted -- until recently, in some states -- entirely on the black market.