Section 4(b) of the Drugs and Drug Trafficking Act 140 of 1992 is unconstitutional and invalid to the extent that it criminalises the use and/or possession of cannabis by a child, as it violates: (1) section 28(2) of the Constitution (best interests of the child are paramount); (2) section 28(1)(g) (right not to be detained except as measure of last resort); and (3) section 10 (right to dignity). This limitation is not reasonable and justifiable under section 36 because: (a) criminalisation does not effectively serve its purported protective purpose; (b) less restrictive means exist in the form of civil interventions under the Children's Act and the Prevention of and Treatment for Substance Abuse Act which are child-centred and rehabilitative; and (c) the harm caused by criminalisation (arrest, detention, criminal records, social stigma, trauma) is disproportionate and inconsistent with children's constitutional rights. The appropriate response to cannabis use/possession by children must be located in social welfare systems that support and rehabilitate children, not in the criminal justice system.