A collection of essays and articles from parties that oppose increasing the availability of and access to cannabis. More than twenty individuals come together in this publication to share their thoughts, the reputable science, and the facts that support their central argument that legalization would increase use by youth and pose risks that are not worth taking. The move to advance legalization is addressed from a pivotal question in the debate: How do we reduce the use of marijuana by youth? This important question is the priority facing policy and decision makers given the solid science on the consequences of use by a youth population. Individuals contributing to this work come from the world of academia; the professions of law, medicine, and public health; and law enforcement; along with individuals and advocates associated with public health initiatives to fight the commercialization of marijuana in the United States, Canada, the UK, and Australia.