The gap in the law

THE Psychoactive Substances Act banned any substance that could affect mental functioning or emotional state by stimulating or depressing the central nervous system.

It exempted alcohol, tobacco and certain medicinal products.

The Home Office said selling nitrous oxide for recreational use risked jail, but legitimate sales of the gas, used in medical and dental operations and for cream whipping machines, were allowed.

However, this was not set down specifically in the Act. Instead, ministers said they were going to rely on case law. Now two trials have collapsed.