"All they're achieving is pushing the stuff down to the black market,'' he said.
There was no rush to stock up at the 12 shops visited by APNZ today in Auckland, and shelves were full of the substances.
"It's like smoking cigarettes, some people were looking for a reason to stop, several customers told me that,'' Ian said.
Legal high shop worker Saddam Mohammed said his manager had let go of staff and he feared he could be next.
"We will have to reduce our working hours. [The shop] was previously open 21 hours but now without the stuff we will be having reduced working hours.''
Mr Mohammed said business had been slow since the first round of substances were banned.
Another shop owner in New Lynn selling psychoactive substances said he was surprised by how slow business had been.
"It hasn't been very busy at all, maybe people think it's happening next week, I don't think people know when it's happening.''
Regular synthetic cannabis smoker Bill Smith, 55, said he thought the Psychoactive Substances Act was a world-leading legislation but now the government had undone their good.
"It was a really positive step to allow peace-keeping citizens to enjoy their drug of choice. I'm now going to be a law-breaker and possibly be prosecuted for it,'' he said.
Mr Smith had bought ten packets of synthetic cannabis, but said he wasn't stockpiling.
Police were today visiting shops to ensure they were aware they would prosecuted if found to be selling the substances tomorrow.
Shop owners said suppliers would be collecting the unsold stock at midnight.
Withdrawal warnings
A toxicology expert said severe withdrawals from synthetic cannabis can cause violence, psychosis and suicidal thoughts.
Christchurch Hospital emergency and toxicology expert Dr Paul Gee warned regular users of synthetic cannabis would experience withdrawals, with most suffering minor symptoms.
"Most users should be able to manage detox at home with advice from their family doctor,'' he said.
Common symptoms include irritability, headaches, mood swings, nausea, diarrhoea and vomiting.
Canterbury and West Coast District Health Board Alcohol and drug services specialist Dr Alfred Dell'Ario said withdrawal symptoms could vary from mild to extreme and last from hours to weeks.
"Most people can cope with mild withdrawal by knowing what to expect, taking extra care of themselves, such as resting and drinking water, and we can provide advice on ways to help people who are agitated and having problems sleeping,'' he said.
"However, people experiencing significant withdrawals including violence, psychosis, suicidal thoughts or anything suggesting significant mood or psychotic illness should be referred to the Psychiatric Emergency Service,'' he said.
