A working guide to public health authority and communicable disease control. Part one covers the police power, its constitutional floor, and what the founding case actually decided. Part two covers federal authority and the statutory-authorization question that now decides these cases. Part three covers isolation and quarantine, the process each requires, and the practical failures that produce non-compliance. Part four covers mandatory reporting and contact tracing. Part five covers vaccination requirements, the state-law exemptions that define them, and the free exercise comparison test. Part six covers liability shields, emergency use authorization, and vaccine injury compensation. Part seven covers emergency declarations and the legislative constraints recently added. Part eight covers litigation strategy on both sides.