An increasing number of countries have, or are moving towards, reforming cannabis policies. New Zealand is also moving in this direction and the government will hold a referendum on the legalization of recreational cannabis in September 2020. To inform imminent public and political discussions it is important to understand how current cannabis use is controlled. Research suggests that cannabis law has been ineffective in NZ. Internationally, informal controls, rather than the law, have been found to shape cannabis use by creating a threshold for normalization, but the attitudes shaping this threshold are unknown.

This study aimed to examine drug acceptability attitudes, specifically students' attitudes towards the illegal use of cannabis and their attitudes towards peers who abstain, sometimes use, or are heavy users of cannabis, to identify the factors that control cannabis use. Using a mixed methods approach, university students recruited their peers (N = 535) to complete a pen and paper survey investigating perceptions towards 3 cannabis user prototypes (abstainers, moderate users, heavy users), concern for legality of cannabis use, and the integration of cannabis into the student culture (perceptions of peers' use, ease of acquisition, and availability). Perceptions of peers' lifetime and regular use were 82% and 38.5%, respectively. Participants rated cannabis as easy to acquire and likely to be available at a typical student social occasion. The majority stated that the law does not deter use (92.7%); participants perceived the law to be soft and that they are unlikely to get caught. Participants' descriptions of the 3 cannabis user prototypes revealed a threshold for normalization. For instance, abstaining was perceived to be associated with positive attributes (such as being studious), linked to being less sociable, and linked to being less likely to be judged. Moderate use of cannabis was perceived to be normal and sociable. Heavy use was perceived to be associated with having negative attributes, such as being addicted, unhealthy, and an underachiever, and negative drug labels.

Our findings revealed that cannabis use is not controlled by the law, but by informal thresholds of control. Moderate cannabis use is accepted whereas heavy cannabis use is not. We extended research by identifying the attitudes shaping these thresholds, in particular that negative outcomes associated with heavy use deters the normalization of this behavior. We argue that policy must be informed by, and build on, these informal controls. The negative perceptions associated with heavy use also raise concerns regarding the well-being of heavy users, and coupled with the ineffectiveness of cannabis law, lend support towards a health model for regulating cannabis. Furthermore, insights into the negative perceptions associated with heavy use could inform health interventions on the types of concerns that will resonate with users.