In reply to M Murray-Benge, and B Porter (June 27), it is startling to read the paranoia from both writers.

Porter claims that the black market will undercut the legal market, where the opposite will happen in reality. A basic understanding of economies of scale means that the legal market will be able to increase its output while keeping costs lower than the small time black market in comparison (consider the medical market too).

In addition, the current black market price for cannabis has increased in price over the past 10 years due to supply and demand. The legal market will be able to undercut the black market rather easily.

Both writers share social issues of drug use, but the irony is lost on them because they have worsened under the current model of prohibition which they are advocating for.

It has failed miserably and change is needed.

The iron law of prohibition states that: ‘as law enforcement becomes more intense, the potency of prohibited substances increases.”

It's actually counter-intuitive to keep pushing the failed current model as drugs get stronger. For example, under alcohol prohibition: Beer and wine, hard spirits, moonshine.

It's time to legalise cannabis and treat it as a health issue if it becomes one.

D Carey, Papamoa