Background and aims: This paper offers a human rights-driven critique of the Psychoactive Substances Act 2016. The particular focus here is on the fact that, while the motivation behind this piece of legislation was the perceived need to address the growing phenomenon of new psychoactive substances, the broad definition of what constitutes a psychoactive substance contained therein means that it also includes psychoactive plants – herein referred to as plant medicines within its ambit. Methods: Through a close analysis of the parliamentary debates and related publications leading up to the Act, it is revealed that these were not part of the problem as constructed, and yet have become entangled in this legislative response to it. Results and conclusions: It is argued that the inclusion of these plants breaches Article 9 of the European Convention on Human Rights, which protects both freedom of thought and religion. It is submitted that the Act should thus be amended accordingly. In support of this argument, the arbitrary difference in treatment of the psychoactive substances, alcohol and tobacco – exempted from the reach of the Act – is highlighted, as is the process by which alkyl nitrites (poppers) were also (eventually) excluded from the legislation, making the claim that much of the lucid reasoning underpinning this latter decision could be extrapolated out to plant medicines. Keywords: Psychoactive Substances Act 2016, plant medicines, new psychoactive substances, human rights, freedom of thought, freedom of religion