Worried about failing a workplace drug test? Depending on your job, you might be within your rights to say no - but not if you're a teacher.
Last week, the Education Council's disciplinary tribunal ruled against a teacher who resigned when asked to take a drug test, after telling her boss she had smoked cannabis in the past.
The tribunal said it amounted to misconduct, although workers in other fields might get away with it.
But there's still a grey area over drug testing and who can say no - while critics believe the current system is broken, and needs a shake-up.
It all depends on your job.
The Supreme Court has said employers can require workers to take drug tests if they work in "safety-sensitive" jobs. This includes work involving transport (truck drivers and airline staff), labouring, primary industries (like forestry, fishing or farming), and even education.
"When they've got employees who are required to exercise judgment, to show responsibility, to use dangerous equipment or be responsible for others who can't be responsible for themselves - like early childhood teachers and things like that - then it's generally accepted in law that people under the influence of drugs and/or alcohol may not be able to discharge those responsibilities in a safe manner," employment lawyer Blair Scotland says.
The legal precedent came about when unions representing Air New Zealand staff tried - and failed - to stop the airline implementing drug testing in 2004.
Professional bodies, like those for lawyers, doctors accountants and teachers, may also require members to adhere to drug-free policies.
However, there may be more wriggle room for those in other fields - depending on their employer's drug policy.
"Most policies that I see make it clear that if you refuse a test without good reason, then that constitutes serious misconduct in and of itself and you can be dismissed for refusing a test. That tends to be the default position. But it would depend on why you were refusing it.
"If your employer said 'I don't care that you're not in a safety-sensitive role, I'm going to impose upon you a random test', well, it might be reasonable to say no in those circumstances."
The Drug Foundation's Ross Bell believes many employers are violating their employees' rights, and even breaching the law.
"We're seeing lots of workplaces that aren't safety-critical doing pre-employment tests, random tests, and I think we're creating a massive problem, a huge breach of privacy, [and] this incorrect assumption that anyone who is using drugs is an unsafe person."
WEEKEND FUN VS WORKPLACE IMPAIRMENT
Critics, including Bell, say the testing regime is flawed because it fails to differentiate between impairment and recreational use.
Because cannabis remains in a person's system for several weeks, someone who used it on a Friday night would still test positive on Monday morning or even weeks later; methamphetamine, on the other hand, takes just a couple of days to clear your system.
Labour's workplace safety spokesman Iain Lees-Galloway said the party supports employers' right to drug test when they suspect an employee is impaired, especially in safety-critical roles, but "it's fair to question whether what you did on Friday night will cause a risk on Monday".
"Let's not equate impairment at work with casual use of cannabis at some point in the past that isn't impacting on your performance at work."
The Ministry of Education's deputy secretary Katrina Casey draws no distinction between the two.
"Teachers are covered by the same laws of the land as everyone else and illegal drug use is clearly unacceptable."
Rose Renton, medical cannabis campaigner, says it's unfair that workers in any field, who used marijuana days earlier, might find themselves in trouble, despite not being impaired on the job.
"If it was me, personally, I'd be happy to have anyone that used cannabis outside of work hours to teach my child, and I think it's utter discrimination that we have something like cannabis be a reason to not employ someone.
"You can drink outside of work hours, and you certainly won't lose your job. You can have a cigarette."
IS THERE A BETTER WAY?
Rose Renton doesn't oppose workplace drug tests for those employees in safety-sensitive fields; however, she says, urine tests are the wrong approach.
"[With] a simple mucus test in the mouth, like a mouth swab, the employers know who's stoned at work, I think is really important in health and safety, and I think that goes across the board.
"You don't want someone flying your plane, or operating heavy machinery, or long-haul truck drivers and those sorts [impaired]. A swab's going to cover them for that safety-wise."
Bell blames drug-testing companies for a "snake oil sales pitch" that's led employers to believe they're fulfilling their health and safety obligations by testing their staff.
"Employers are searching for a silver bullet, this easy fix - if you pee in the cup, we're protecting ourselves - and they're not doing the things that good employers should do, which is trying to do a whole lot of different things to create a culture of safety in their workplace.
"You don't want to tolerate people being impaired at work, whether from illegal drugs or alcohol, but there's other ways to get to that point without going down that humiliating drug-testing route."
Bell says workplaces should be working with staff on drug education, processes for raising concerns with peers and management, and ways for staff to disclose their drug use and receive support."
He adds that since the 2004 case, Air New Zealand has become an industry leader with its drug and alcohol policies, including the support it offers to staff.
Scotland, the employment lawyer, agrees that bosses need to do more than just drug tests.
"If you're really serious about helping people out and having a drug-free environment, you say to your people 'look, if you front up ... and say 'I've got an issue with drugs, I need help with it',' I think it would be reasonable for an employer to try and accommodate that.
"I'm not talking about paying for you to go in a nice programme down in Hanmer Springs or anything like that. But if a person wants to volunteer for help, should they be punished or should they be helped?"