It is illegal because not enough people have come forward and demanded otherwise.

"83 million Americans admit to having tried it (Cannabis)"*

Do the math and out of a total population of 299,814,291 thats over 27.6% of us.

The problem is that too many of that 83 million remain silent, they may not be current pot smokers but it is up to those of us that are to make it an issue and for them to stand behind us.

Substance Abuse and Mental Health Services Administration, Summary of Findings from the 2001 National Household Survey on Drug Abuse (Rockville, MD: Department of Health and Human Services, 2002), Table H.1, from the web at
http://www.samhsa.gov/oas/NHSDA/2k1N...ppendixh_1.htm