My opinion is that once Government gets involved in controlling substances people would still buy from the black market due to potency being non existent. California is actually closing down a lot dispensaries due to community and Government pressure.
Medical canna in Aus would never be allowed for recreational use and be strictly controlled and still hard to get . How would pensioners and people in regional coastal areas with low job prospects be able to survive keep a roof over their heads,, they would have to pedal harder drugs. Australia will never follow down the same path of the US.