This article considers the increased use of mandatory sentencing provisions in a range of jurisdictions, including Canada, Australia, the United States, and United Kingdom/Europe. It finds that, whereas some courts have struck out mandatory sentencing laws, often mandatory minimum penalties have been validated. This jurisprudence is considered through a range of themes, including notions of arbitrariness, the doctrine of proportionality, the relevance of objectives of the criminal justice system, and broader questions regarding the separation of powers.