Nitrous oxide is capable of being a “psychoactive substance” for the purposes of the Psychoactive Substances Act 2016. If that substance is in the form of a “medicinal product” and used medicinally (or it is intended to be used medicinally) then – in England and Wales – the product would appear to be subject to the regulatory regime enacted under (principally) the Human Medicines Regulations 2012 and exempted under the PSA 2016. There have been occasional reports that suggest that super-sized canisters of nitrous oxide are “legal”. Given the judgment of the Court of Appeal (Criminal Division) in R v Chapman  EWCA Crim 1743, para.32, this is a highly dubious proposition if “….the purpose for which it was intended to supply the canisters was purely recreational with nothing whatsoever to do with health. This last feature coupled with the fact that the gas was intended to be used in circumstances which were not beneficial to health, indeed import some risk to health, was sufficient to take it outside the definition of medicinal product whatever label may have been on the boxes in which the canisters were originally packed.” Supplying, intending to supply, importing, exporting, producing, and possessing in a custodial institution a non-exempted “psychoactive substance”, are activities that are capable of being offences under the PSA 2016. As with all commentary on the law, the usual caveats apply!