The Home Office has published a commendably detailed review into the operation of the Psychoactive Substances Act 2016 since it came into force on 26 May 2016 [Link].  Its conclusions (only summarised below, p.69) are:

1. To put an end to the open sale of NPS: This appears to have been achieved although the main source of supply for NPS “is now likely to be street dealers, particularly for synthetic cannabinoids.”
2. To put an end to the game of ‘cat and mouse’.  This does not appear to have been achieved (based on a small number of observations from the Forensic Early Warning System).  “Novel drugs which are not controlled under the MDA have continued to emerge”.
3. To reduce the number of people using NPS.  This appears to have been achieved for the general adult population, “with a significant reduction in NPS use since the Act, particularly among young adults”.  However, what has not changed significantly is the use of nitrous oxide among adults and the use of NPS among children.  As for NPS use among vulnerable users, including the homeless, the evidence “is mixed” with “some displacement from synthetic cannabinoids to ‘traditional’ controlled drugs”.  In prisons, “the PSA does not appear to have restricted the prevalence of NPS, with use of synthetic cannabinoids in particular appearing to have increased since the Act was introduced”.
4. To reduce the various health and social harms associated with NPS. “This appears to have been achieved in the main, although there are some specific areas of concern…. [W]hile there has been a reduction in NPS-related deaths across England and Wales, there has been a considerable increase in Scotland since the Act has been introduced”.

The Review states that the decisions of the Court of Appeal in R v Chapman [2017] EWCA Crim 319, and R v Rochester [2018] EWCA Crim 1936, are “binding” (p.4, p.14).  However, care must be taken when determining the points of legal principle that are truly “binding”.  In Rochester, the Court made it clear that whether something is capable of producing a psychoactive effect “is a question of fact, no doubt sometimes assisted by expert evidence” [para.19; emphasis added].  The legal principle, which is ‘binding’, is that “section 2 of the 2016 Act does not distinguish between direct and indirect effect when it defines a psychoactive substance as one which produces a psychoactive effect” [para.25; emphasis added].  The potential implications of this decision extend beyond cases of nitrous oxide presented in canisters for catering use.