EVERY major government study for over 50 years has concluded that marijuana should be decriminalized or legalized.
The National Commission on Marihuana and Drug Abuse (the Shafer Commission) had 13 members, most of them hand picked by President Nixon to affirm his view of marijuana as a menace. After long study, they opted for the truth instead.
It's hard to imagine from today's rhetoric, but their 1972 report (reaffirmed by the National Academy of Sciences in 1982 and also ignored, this time by President Reagan) is as valid today as it was then. Some extracts:
"We ask the reader to set his preconceptions aside as we have tried to do, and discriminate with us between marihuana, the drug and marihuana, the problem.
"Recognizing the extensive degree of misinformation about marihuana as a drug we have tried to demythologize it.
"No valid stereotype of a marihuana user or non-user can be drawn.
"The most notable statement that can be made about the vast majority of marihuana users - experimenters and intermittent users - is that they are essentially indistinguishable from their non-marihuana using peers by any fundamental criterion other than their marihuana use.
"Young people who choose to experiment with marihuana are fundamentally the same people, socially and psychologically, as those who use alcohol and tobacco."
"Most users, young and old, demonstrate an average or above-average degree of social functioning, academic achievement, and job performance.
"Neither the marihuana user nor the drug itself can be said to constitute a danger to public safety."
Someone Is Lying
The public must decide who is lying. The world's leading medical journal, The Lancet, has repeatedly called for legalization and rebuked the government for exaggerated claims about health risks. 
"It would be reasonable to judge cannabis less of a threat to health than alcohol or tobacco. On the medical evidence available, moderate indulgence in cannabis has little ill-effect on health." - Lancet
"Sooner or later politicians will have to stop running scared and address the evidence: cannabis per se is not a hazard to society but driving it further underground may well be." - Lancet
"As someone acknowledged as a specialist in drug actions on the brain, I know a great deal about cannabis and how it affects its users, and I know that there are simply not the facts to stand up outrageous statements like this.
" It is headline-grabbing rubbish.
"When I advised the House of Lords committee five years ago that cannabis was not as damaging as, for instance, regular smoking or drinking, no one wanted to know about our findings.
"Cannabis is simply not as dangerous as it is being made out to be."
- Professor Les Iversen, Department of Pharmacology at Oxford University, author of: The Science of Marijuana (extracts from The Evening Standard, May 6, 2003)
Why Is Marijuana Illegal?
... El Paso Morning Times for Friday, June 4, 1915 ... page 16:
" Under an emergency clause the city council adopted the marihuana ordinance prohibiting the sale, barter, exchange, giving away and having in possession the deadly drug. The ordinance makes it unlawfully for any person, firm or corporation within the city limits to handle the drug. The grounds for the emergency passage of the ordinance, it was stated, were the dangerous and powerful properties of the drug and the increasing sale of it in the city. Mayor Tom Lea instructed City Attorney W. B. Ware to act in conjunction with the police in seeing that the ordinance was enforced. A punishment by fine not to exceed $200 is provided.
It is due to the efforts of Chief Deputy Sheriff Stanley Good, Sr., that the city took steps to prohibit the traffic in marihuana. The drug is considered the most deadly of any known and while there are laws prohibiting the sale of morphine and kindred drugs there was never any provision made against the dealing in marihuana. Marihuana is known to create in users a lust for human blood. The most atrocious murders committed in El Paso have been attributed to marihuana fiends.
The sales of the drug recently assumed such alarming proportions that Good took the matter up with the city government."
... numerous internet sites contend that El Paso was the first to enact such an ordinance. The date given for the enactment is variously stated as being 1913, and sometimes 1914. I checked the Charter and Penal code of the city of El Paso, 1917 and found codified in Section 53 thereof "Sale of Marihuana Prohibited: It shall be unlawful for any person, firm, corporation or association of persons to sell, barter, exchange, give away, or have in his possession, within the city limits of the City of El Paso, Texas, any marihuana of Indian hemp." Section 54 provided "Any person who shall violate any provision of section (53) of this ordinance shall be punished by a fine of not more than Two Hundred ($200.00) Dollars." The citation for these sections is given as June 3, 1915; Book E-2, p. 611, sec. 1 and 2.
I can find nothing showing that the City of El Paso first enacted anti-marihuana legislation prior to June 3, 1915.
Legal Reference Librarian
The University of Texas at El Paso
DPFT note: Our thanks to Charles Gaunce for his response to our inquiry via Prof. Buford Terrell. Others have noted that the targets were almost always Mexicans who were competing for scarce jobs with Whites. The racist theme is explored in detail by Bonnie, Richard J, et al. in The Marijuana Conviction: A History of Marijuana Prohibition in the United States. <http://www.drugpolicy.org/library/bookstore/1891385062.cfm>
The same nonsense was offered by H. Anslinger (head of the Federal Bureau of Narcotics [FBN] ) in testimony to Congress to justify marijuana prohibition in 1937. (People were warned in the 1920s not to use cocaine or heroin because they were the "gateway" to marijuana.) By 1954 Anslinger would testify that marijuana prohibition must be continued because marijuana made users so peaceful that they would not fight communists. Sigh.