And so does India. Marijuana was legal in India til 1985 then US government forced Indian government criminalize it.
Prohibition has many causes. The international treaty / 'Single Convention' was the first international treaty to prohibit cannabis.
The Single Convention on Narcotic Drugs of 1961 is an international treaty to prohibit production and supply of specific (nominally narcotic) drugs and of drugs with similar effects except under licence for specific purposes, such as medical treatment and research. As noted below, its major effects included updating the Paris Convention of 13 July 1931 to include the vast number of synthetic opioids invented in the intervening thirty years and a mechanism for more easily including new ones.
https://en.wikipedia.org/wiki/Single_Convention_on_Narcotic_...
Watch "Reefer Madness" - it's reflective of the mindset these policymakers grew up with.
If you want to understand where that mindset ultimately came from, look at the history of cocaine prohibition - it boils down to racial politics.
It is only in modern times as I read more I learned the truth. Not everyone has time to educate themselves on these issues which many not concern them.