This is a groundbreaking book that offers key stakeholders, policy makers and professionals a much needed resource to understand the need to provide effective and humane treatment of drug users with drug addiction problems (drug dependants) who fall within the criminal justice system in Malaysia. This book begins with a narrative description of the historical evolution of drug abuse in Malaysia: beginning from the opium trade in the 18th century, with the exodus of the Chinese immigrants to Southeast Asia and Malaysia as labourers in the late 19th century which brought along the problem of opium addiction to the Malay Peninsula, to the 1970s which saw a transitional change from opium addiction to heroin and the rise in amphetamine-type-stimulant (ATS) abuse in Malaysia as the 21st century drug problem. It then provides an overview of Malaysia’s prohibition approach by waging the rhetorical War on Drugs, including the development of Malaysia’s punitive drug laws and the recent paradigm shift towards a more rehabilitative approach in drug treatment. Over the years, a considerable number of High Court cases have challenged the legality of the detention of drug dependants for treatment at Puspen via a court-mandated order. This book further presents a commentary that is founded upon the legal challenges brought about by such unlawful detention, illustrated by judicial decisions of Malaysian judges regarding the constitutional rights of the drug dependants enshrined under Article 5 of the Federal Constitution.