"This Administration firmly opposes the legalization of marijuana"

From the new National Drug Control Strategy, here's our government's official position on why marijuana must remain illegal:

We have many proven methods for reducing the demand for drugs.  Keeping drugs illegal reduces their availability and lessens willingness to use them.  That is why this Administration firmly opposes the legalization of marijuana or any other illicit drug. Legalizing drugs would increase accessibility and encourage promotion and acceptance of use.  Diagnostic, laboratory, clinical, and epidemiological studies clearly indicate that marijuana use is associated with dependence, respiratory and mental illness, poor motor performance, and cognitive impairment, among other negative effects, and legalization would only exacerbate these problems.

Oh yeah? Well, empirical studies also clearly indicate that marijuana prohibition is associated with drug trade violence, funding of dangerous criminal organizations, environmental destruction, unsustainable criminal justice costs, suppression of evidence regarding medical benefits, among other negative effects, and continued criminalization would only exacerbate these problems.