I have heard horror stories from people who used the drugs, about the desperate state it had left them in.
In April, local Hamuera Hodge told the Rotorua Daily Post he was once hooked on heroin, but synthetic cannabis is much worse and should not be seen on the city's streets.
He said three of his adult children smoked synthetic cannabis when it was legal and all had experienced personality changes and had trouble concentrating.
"I know of families with children in mental institutions and I know of people who have hung themselves because of these drugs," he told us.
Anything that dangerous should undoubtedly also be illegal. Yes, some people will still continue to use it but there will be others who decide not to try it because it is illegal.
Making it illegal is a strong warning that it is not safe.
No one knows what is in synthetic cannabis products or what the combination of those ingredients will do.
The law does allow certain products to be sold legally if the producer can prove it is safe.
That is the sensible way to deal with it.
Until it is proven safe we should be doing everything possible to discourage people from using the drugs.