The bill passed with the support of National, ACT, New Zealand First, and Labour, though all but National raised concerns with the bill that they hoped would be addressed in a statutory review.
The Greens and Te Pāti Māori did not support the bill.
The legislation gives police powers to undertake random roadside saliva tests, similar to drink-driving enforcement.
Drivers who return a positive result will have their saliva sample sent for further laboratory testing. If that subsequent test finds qualifying drugs and an indication of recent use, the drivers would be issued a fine and demerit points.
Two positive roadside tests would be required before a driver is prohibited from driving for 12 hours.
Under changes made at the committee stage, drivers will be able to challenge the result once an infringement notice has been issued following a positive test, by paying a private analyst to test the oral fluid sample.
Transport Minister Chris Bishop acknowledged it was not the first time a government had attempted to pass such legislation.
"We know that they're [drugs] a major factor in many road deaths and serious injuries. We had a go back in 2022, but the approval criteria was incompatible with commercially available devices. We're now making sure that police are equipped with roadside oral fluid screening as a road safety tool to enable the enforcement," he said.
"I think we will look back in five to 10 years and we will say, 'what was the fuss about?'"
The Attorney-General's report into the legislation, written in July 2024, found it was inconsistent with parts of the Bill of Rights Act, specifically the right to be secure against unreasonable search and seizure, and the right not to be arbitrarily detained.
Judith Collins considered the Bill's aim as a deterrent to, and a restraint on, drug-impaired driving to be a sufficiently compelling public policy objective to justify the use of some search and seizure powers.
However, she found the intrusion on privacy was not proportionate to the public interest objective.
"The intrusion on an individual's privacy that arises from the taking of a bodily sample for the first oral fluid screening test appears disproportionate where there is no basis to suspect the individual driving is under the influence of an impairing drug," she wrote.
Labour raised these concerns at the third reading of the Bill, although it supported it.
"Labour has been deeply concerned about the concerns that have been expressed right throughout by the Attorney-General, around the potential breaches that an individual who might be going about their normal business, any day of the week, any time of the week, would be effectively detained at the roadside," said Labour's transport spokesperson Tangi Utikere.
ACT supported the bill but was looking forward to a statutory review of the legislation in a few years' time, to see if its concerns would be addressed.
MP Cameron Luxton said he had concerns about the time which someone could be delayed from undertaking their lawful business, and the ambiguity around whether that person could be required to accompany a police officer to a further location than what would be deemed necessary "by any reasonable person".
He also said officials had acknowledged "randomness" was a euphemism for a strategic approach.
New Zealand First also raised concerns about the time delay between the two tests, and the power of the State to detain someone, but ultimately supported the bill as well.
Concerns for Greens, Te Pāti Māori
The Greens, however, opposed the bill.
MP Lawrence Xu-Nan said while nobody should drive while impaired, there was a lack of evidence the bill would address the root cause of dangerous driving or drug harm.
"The oral fluid test cannot prove impairment. That's one of the major issues because it is not like alcohol where the relationship between breath and blood levels is more strongly correlated with impairment," he said.
"Yes, there may have been some things that have been said in terms of the accuracy of this particular oral test, but to be honest, it doesn't actually offer the same level of reassurance as what we're currently seeing in terms of the breath alcohol test."
Xu-Nan also raised concerns of inconsistencies of different drugs' pharmacological effects, and their interactions with the human body.
Te Pāti Māori MP Takuta Ferris said the party also did not support driving under any impairment, but the bill would exacerbate the presence of rangatahi Māori in the justice system.
"Police profile rangatahi Māori. That's why they get pulled up more than any other rangatahi group," he said.
The roadside drug testing regime is expected to be in place by December, with the government wanting police to undertake 50,000 tests a year.
