Again, the gateway theory has been debunked so many times it's not worth discussing anymore. Further, there are other side effects of the current policy- the marginalization of convicted felons (and other negative consequences of imprisonment, especially in light of the high rates of recidivism), the promotion of the black market and organized criminal activity in general (consider the negative consequences of alcohol prohibition in America in the 20s), the disintegration of the family (when non-violent offenders are imprisoned..this also relates to the problem of learned criminal activity in prison), possible adverse health effects (uncontrolled substances that will be used regardless are far more likely to be laced with other more serious and addictive drugs), and (again) potentially higher use among minors- that ought to be considered. This is ignoring entirely the cost of the current (international) policy, and the other, more effective and cheaper, methods of dealing with matters of public health, like addiction.