Drug and rehabilitation workers are warning of a black market for legal highs emerging, following the banning of the drugs.
The Psychoactive Substances Bill received overwhelming cross-party support with 119 members voting in favour of the proposal last night. There was just one vote against.
The new law restricts dairies, grocery stores, petrol stations and alcohol retailers from selling synthetic cannabis.
Any retailer caught selling the banned substance to under 18s will face a fine or up to two years in prison.
Te Menenga Pai Trust manager Carole Maraku said the law change, however, will not be the end of the synthetic drugs.
People will have stockpiled the drugs and will now be preparing to sell them illegally, Ms Marakau said.
Last night, associate Health Minister Todd McLay said outlets that still wanted to sell the synthetic cannabis would need a special licence. But the licence comes at a significant cost.
"This bill is squarely about public safety and will ensure that the onus will be on anyone wanting to produce a psychoactive product to show it poses no more than a low risk of harm."
Mr McLay also acknowledged the considerable amount of work done by MP Peter Dunne in getting the bill to Parliament.