Labour already is reminded regularly of the reality of the responsibilities of government. Thus it is with the issue of medicinal cannabis.
Leader Jacinda Ardern in Opposition was emphatic before this year's election. In one of the television debates she said, when asked whether she would legalise cannabis for medicinal use, ''absolutely yes''.
The Misuse of Drugs Amendment Bill tabled in Parliament last week, however, is short of what that answer would imply.
It allows for a regulated domestic cannabis industry, makes it easier to access medical cannabis products, allows the terminally ill to use illicit cannabis and moves to establish a body to set standards.
It also falls short of Green MP Chloe Swarbrick's Bill allowing people to grow cannabis for medicinal purposes.
The Government and Health Minister David Clark have themselves in a tangle. There are implications in going full ahead on legalising cannabis for medicinal use, and a staged and careful approach makes sense.
Nevertheless, this makes matters messy. While that is unfortunate, there seem no other wise options. Caution over cannabis is required. Eventually, Ms Ardern's wish and her answer should come to pass. Extracts for medicinal purposes should become available.
Against this background, it is unsurprising that Dr Clark's messages are mixed. Personally, he says he will support Ms Swarbrick's Bill to first reading so it can be tested, revised and submissions received from medical experts.
But as Health Minister he said the Government was not adopting the Bill. ''I'm the Minister of Health ... I have to take responsibility for ensuring that products are getting to market have evidence around them''.
Indeed. It is all too easy to become caught up in fervour and leave the science, the experts and the processes behind. Policy should be based on evidence not emotion.
The faith in, and discretion given to, police is also far from ideal. They have for years been placing less emphasis on cannabis in its ''recreational'' form. But uneasiness over relying on police to turn a blind eye is evident, especially when discretion is mandated for the terminally ill. Police could, as well, be caught in unenviable positions as the lines between cannabis for health and other uses are blurred.
Police certainly did their case no good when a drug squad last week pulled out an experimental plot of medicinal cannabis that had official approval.
Clearly, popular demand for medicinal cannabis is driven by those who feel its benefits, and the high-profile pleas of union leader Helen Kelly before she died advanced the cause. Background demand will also come from those seeking recreational use.
The irony, of course, is that a primary medicinal ingredient, CDB, does not have psychoactive effects. That is caused by the THC, and medicinal cannabis should be low in this.
Evidence for cannabinoids (the ingredients in cannabis) for chronic pain and spasm has been described as moderate, and that for other conditions - including nausea and vomiting - as low quality. Access to pharmaceutical-grade medicinal cannabinoids is limited and expensive, and it is little wonder many doctors are cautious.
Medicinal cannabis as a stalking horse for legalising cannabis is a concern. The effect of the drug on teenage brain development and its correlations with mental health issues suggest adding another dangerous substance to our legal cocktails might be damaging. There are already enough detrimental health problems from tobacco and alcohol. Legalisation of cannabis is likely to increase its already (perhaps about 10% of the population) high use.
Nonetheless, it might be possible for New Zealand - as is happening in Australia - to develop a medicinal cannabis industry to produce extracts that are close to free of THC while containing benefits from other cannabinoids. Progress can be made towards medical cannabis becoming a realistic treatment option.