Laws should be certain and clear
The Misuse of Drugs Act 1975 is not fit for purpose. The law is 45 years old.
In 2019 amendments were made which (effectively) direct the police to use discretion for instances of cannabis possession (i.e. ignore the law) unless it is in the best interests of society to prosecute an individual.
The law is not certain or clear when the police are directed to use such a high level of discretion.