COVID-19 vaccinations are lagging in the United States, and in an effort to curb rising cases, some states, universities, and other entities have instituted vaccine mandates for its employees and other affiliated individuals. In contrast, other states like Arkansas, Montana, Florida, and Utah have passed legislation prohibiting state agencies or businesses from requiring vaccination. Professor Dorit Reiss of UC Hastings Law explains the constitutionality of vaccine requirements and the open question of whether vaccines approved under emergency use authorization may be mandated. She explains the divergent paths some states, employers, and universities have taken and the mounting legal challenges against such laws and policies.