Denver voters are considering Initiative 100, which seeks to give cannabis a similar status to alcohol under city ordinances (while leaving the state law in place), much to the consternation of Washington Park City Council member Charlie Brown.
Marijuana is legal for medical purposes under state law in places like California and Colorado (and ten other states whose names do not begin with "C"), but illegal in much of the rest of the nation and under federal law. Why is it illegal for marijuana to be perscribed by a doctor to treat an illness? Because it is a Schedule I drug under the federal Controlled Substances Act, as it has been since 1970.
Britain, in contrast, rescheduled cannabis to its schedule C (roughly equivalent to the U.S. schedule III) last year, and a researcher in Canada (which has recently decriminalized possession of small quantities of cannabis for medical use), has discovered that it may have health benefits similar to Prozac. Cannabis is effectively decriminalized in small amounts in Portugal, the Netherlands and Germany.
On the other hand, Bali, Indonesia, mets out harsh sentences to pot mules, and the United States is often equally harsh.