Illegal drug use is here to stay. Human beings have used mind-altering chemicals for at least as long as we've cultivated crops, and if the US experiment with prohibition of alcohol in the 1920s taught us anything, it's that criminalizing a product with such huge demand will do very little to stop people using it.

http://arstechnica.com/journals/science.ars/2007/03/23/assesing-the-harm-of-illegal-drugs