Parliament has approved a modification to the Swiss narcotics law that will allow studies of recreational cannabis use in the country’s largest cities.

Both houses approved the change to the law on Wednesday following debate over whether the cannabis distributed to users had to be of local or organic origin.

The right-wing Swiss People’s Party saw this as an opportunity to support the country’s agriculture sector. Parliament ultimately decided that Swiss and organic cannabis should be used as far as possible.

The vote paves the way for scientific studies on the effects of the controlled use of cannabis to be carried out. This is intended to help evaluate the effects of new regulations on the recreational use of cannabis and ultimately, combat the black market distribution of cannabis.

One third of the Swiss population is reported to have already smoked marijuana and some 200,000 people use it on a regular basis. Several cities including Bern, Geneva, Zurich and Basel have shown interest in conducting studies to better understand the current cannabis market.

Any pilot projects that involve the distribution of cannabis will be regulated by a strict framework along with an enforcement order. Participation in pilot projects will be limited to cannabis users who are at least 18 years old. The health status of participants will be closely monitored.

Trials will not last for more than five years and the number of participants should not exceed 5,000 per trial.