As of this morning, all interim approvals for psychoactive products have been revoked, effectively meaning the use, sale or manufacture of the products is now illegal.
In the days leading up to the ban, police have visited the nine retailers in the greater Dunedin area to remind them of the law change.
''We have been hammering on the doors making sure they understand their obligations,'' Dunedin Clutha Waitaki area prevention manager Inspector Mel Aitken said.
Those obligations include making sure stock was removed from shelves.
Police have also been providing ''community reassurance with high-visibility patrols around these locations''.
''We want to make sure nothing untoward happens once this stuff is taken off the shelves.''
It was too early to say if those who continued to consume the product would be arrested, but she acknowledged ''we need to tread carefully''.
''Clearly, we have concerns around the health aspects and people suddenly going cold turkey.''
Asked if police were anticipating a spike in crime following the withdrawal of the products, she replied, ''We are about prevention and we do see it as a risk and we are putting measures in place to prevent it from happening. We won't be sitting back and doing nothing.''
The New Zealand Drug Foundation has urged police to hold off prosecuting people for the next six months for possessing psychoactive products.
Executive director Ross Bell said when BZP was reclassified as a class C drug in 2008, there was a six-month grace period where police did not chase people for possession.
''This worked well to allow people the space and time to figure out where and how to get help.''
Mr Bell told the Otago Daily Times that following the BZP ban, there was no spike in crime, ''because when BZP was banned, it was replaced immediately with other legal highs''.
''It is hard to know what will happen in that regard ... this is uncharted territory.
''These products will go to the black market and be replaced with nothing.''
For help: Alcohol and Drug Helpline - 0800 787-797.
