The Psychoactive Substances Act had been due to come into effect on April 6, but has now been postponed. r.classen/Shutterstock

A controversial piece of legislation designed to place a blanket ban on all so-called psychoactive substances in the U.K. has been indefinitely shelved after concerns were raised about its enforceability. Confusion has reigned ever since the act was first announced last year, largely because scientists and politicians have struggled to agree on which substances the new law actually prohibits.

Known as the Psychoactive Substances Act, the bill was initially drafted as an attempt to outlaw legal highs – substances that are sold legally simply because they have not yet been banned. Government ministers had become concerned that these drugs, also known as new psychoactive substances (NPS), were being synthesized faster than they could be outlawed, leading to a continual game of cat and mouse.

Attempting to resolve this situation in one fell swoop, the government drafted the bill in 2015, but have since been criticized for taking a sledgehammer to a situation that required a more delicate solution. The act initially proposed to ban the use, sale, and possession of any substance capable of producing a psychoactive effect or generating an emotional response.

Such a broad scope would therefore include the likes of alcohol, coffee, nicotine, and a range of medications. Because of this, the government drafted a list of substances that would be exempt from the bill, while also commissioning the Advisory Council on the Misuse of Drugs (ACMD) to help them narrow down the definition of a psychoactive substance.

The government initially believed it had banned poppers, but scientists have informed them otherwise. Image via Wikimedia Commons

The outcome of this process was a new focus on substances that have a direct effect on the brain and central nervous system (CNS). However, this too proved to be highly problematic, as many drugs fall into a gray area whereby their impact on the CNS may be described as indirect.

For instance, alkyl nitrates – better known as poppers – were initially widely reported to be banned by the new legislation, although the ACMD later advised the government that these drugs only indirectly affect the CNS, and should therefore not be outlawed. As such, it seems the government and law enforcement agencies simply do not know which substances to criminalize, making it impossible to prosecute offenders.

With no clarification on what counts as a psychoactive substance, the government has canceled the implementation of the act, which had initially been scheduled to become law on April 6. No new date has yet been set for the implementation of the bill, although the Home Office insists it still plans to bring the new law into effect at some point this spring.

The main reason cited for this decision was the clear difficulty faced by “law enforcement in their ability to drive forward the legislation.” Similar complications were experienced by police in Ireland following the recent introduction of a similar bill there. According to media reports, there have been very few prosecutions relating to this law because of difficulties proving whether or not a substance is psychoactive.

Furthermore, while hospital admissions for adverse reactions to NPSs have dropped in Ireland since the change in legislation, many claim this is simply because people who take these drugs are now reluctant to seek medical attention for fear of being prosecuted. As such, critics of the act say it is likely to increase rather than decrease public health risks.