 Where decriminalisation has been implemented, such as in several states in Australia and United States, as well as in Portugal and the Netherlands no, or only very small adverse effects have been shown on population cannabis usage rate.The lack of evidence of increased use indicates that such a policy shift does not have adverse effects on cannabis-related harm while, at the same time, decreasing enforcement costs.In the last few years certain strains of the cannabis plant with higher concentrations of THC and drug tourism have challenged the former policy in the Netherlands and led to a more restrictive approach; for example, a ban on selling cannabis to tourists in coffeeshops suggested to start late 2011.