Why did New Zealand's referendum to legalise recreational cannabis fail?

New Zealand recently held the world's first national referendum on cannabis legalisation involving a detailed bill to regulate retail sale and supply of cannabis for recreational (non-medical) adult use (i.e. the Cannabis Legalisation and Control Bill; CLCB). The referendum generated significant domestic debate and lobbying from both sides of the issue. The CLCB was narrowly defeated, with 48.4% voting to support versus 50.7% opposed. In this commentary, we discuss the referendum campaigns and other political and social factors that may have contributed to the result. Voting patterns appeared to largely follow traditional conservative-liberal, urban-rural and age divides. The referendum format created a public campaigning environment that encouraged persuasion and selective use of evidence rather than rational discussion of all the evidence and related knowledge gaps. The self-imposed neutrality of the centre left Labour Party and its popular leader may have been a decisive factor in the narrow defeat. It did not appear to be the case that anti-CLCB groups outspent the pro-CLCB movement in online promotional advertisements, and the leading digital media appeared largely neutral or mildly in favour of reform. The recent New Zealand experience illustrates the uncertainties of attempting to achieve cannabis law reform via a public referendum vote.