But there have been calls for a review of the law after the first prosecutions involving laughing gas were dismissed by the trial judge, following successful legal challenges.
The wide-ranging law banning so-called legal highs came into force in May 2017 to stamp out the distribution, sale and supply of substances capable of producing a psychoactive effect.
A number of substances, including alcohol, tobacco, caffeine and medical products were excluded from the legislation.
Last month two men accused of trying to sell nitrous oxide at the Glastonbury music festival walked free from court after their lawyer argued the gas was exempt from the new psychoactive substance legislation, because it was also used for medical purposes.
Earlier this week a second case, involving an alleged supplier in London, also collapsed after the prosecution’s own expert witness admitted nitrous oxide was exempt under the current legislation.
Maybe MPs did mean to ban nitrous oxide. But the entire point of the CPS is to have someone deciding what should be prosecuted. And they should, above all, know what the actual law is.