Public health law safeguards the health and safety of the population, promoting the human right to life and health, and the realization of social justice. There is sometimes a tension between public health regulation to promote community health and protecting individual liberty and autonomy. Governments must balance the common good with individual freedoms. In many countries, there are constitutional rights to health or to life that provide a positive duty on government to advance the right to health. Governments have multiple legal tools available to improve the public’s health and safety, ranging from the economic power to tax and spend, to the authority to alter the environments in which people live, through to direct and indirect regulation, including, where necessary, deregulation. Although the law can be a powerful agent for change, intervention can also raise critical social, ethical, or constitutional concerns. These issues are illustrated through four brief case studies on infectious diseases, non-communicable diseases, unintentional injuries, and violence to self or others.